At Mar-a-Lago on a Wednesday evening last month, Donald J. Trump mingled with partygoers, greeting his supporters and making small talk. The country star Lee Greenwood sang “God Bless the U.S.A.,” and the former president’s oldest son, Donald Jr., gave a speech.

The elder Mr. Trump was presiding over a cocktail reception for about 150 guests to celebrate the public debut of Trump Media & Technology Group, the parent company of his social media app, Truth Social. Trump Media’s share price had soared in its first day of trading, adding billions of dollars to Mr. Trump’s wealth.

But the party was far from lavish. Guests munched on cookies emblazoned with the letters DJT, the company’s stock symbol. They were invited via the free Paperless Post app and told they couldn’t bring a plus one, according to a copy of the invitation.

Mr. Trump was not shy about the frugality. A benefit of Truth Social, he told guests, is that it is “not very expensive to run.”

From the moment Trump Media was founded in 2021, Mr. Trump has treated it as a low-cost, low-effort venture. While he once served as chief executive and owns nearly 65 percent of the company, he has been only marginally involved in its day-to-day operations, mostly posting on Truth Social and delegating the business to others. At times, he considered working on competing ventures, according to court filings, corporate records and five former employees and others familiar with the company.

Mr. Trump now finds himself in a strange position, with his financial future hinging on an endeavor that he sometimes seemed indifferent toward. Trump Media’s Wall Street debut in March turned Mr. Trump’s stake into a more than $5 billion bonanza. It has tripled his net worth, providing a potential monetary lifeline as he runs for president and grapples with steep legal bills tied to the civil and criminal cases against him.

Yet his newfound fortune is precarious. For years, Trump Media, founded by two former contestants of “The Apprentice,” was entangled in a Securities and Exchange Commission inquiry and an insider trading investigation. It has no products beyond Truth Social, which has a small audience and generated $770,000 in revenue in the first three months of the year while losing $328 million. Still it has a market valuation greater than $7 billion.

“It’s one of the most obvious worthless stocks I have ever seen,’’ said Alan Jagolinzer, an accounting professor at the University of Cambridge in England.

Mr. Trump’s prosperity is merely paper wealth. Trump Media’s share price is volatile, fueled by amateur traders who often ignore business fundamentals. And Mr. Trump cannot sell his shares until September, under a provision common in merger agreements and public offerings, which restricts him and other large investors from immediately cashing in on shares. If he sells the stock, smaller shareholders may take it as a signal to flee.

“The risk of the Trump Media fortune is very, very high,” said Mike Stegemoller, a finance professor at Baylor University. “You’re now dealing with a fortune that is somewhat disconnected from reality.”

Representatives for Mr. Trump didn’t respond to requests for comment. Shannon Devine, a Trump Media spokeswoman, said The New York Times’s reporting on the company was “filled with misleading insinuations and outright falsehoods, and supported by supposed experts who just happen to share the authors’ biases.”

Committed, or not?

Trump Media was not Mr. Trump’s idea.

After Mr. Trump left the White House in 2021, two contestants from the second season of his reality TV show “The Apprentice” — Wes Moss and Andy Litinsky — pitched him an idea for a social media platform built around his brand.

Mr. Trump had just been barred from Twitter after the Jan. 6 riot at the Capitol. Mr. Moss and Mr. Litinsky argued that if the former president built his own social media company, he wouldn’t be deplatformed again.

In February 2021, Mr. Trump signed a deal with the duo to start Trump Media. He received a 90 percent stake in the venture and the title of chief executive. All he had to do was give it his name.

Mr. Moss and Mr. Litinksy oversaw the hiring of engineers to build Truth Social, which would largely cater to conservatives, with the aim of releasing the app in about a year.

But before the app was even built, Mr. Moss and Mr. Litinksy wanted to take Trump Media public through a merger with a “special purpose acquisition company.” SPACs are shell corporations that raise funds by offering shares on Wall Street, then look for private companies to combine with, allowing those companies to bypass the scrutiny that typically comes with an initial public offering.

Mr. Trump left the details to the “Apprentice” duo. Mr. Litinsky, a right-wing radio personality, cold-called hundreds of SPACs to strike a deal. It was “almost no different than picking up the phone to sell insurance,” he testified in federal court last month, in a legal case tied to the merger process.

He eventually found Patrick Orlando, an ex-Deutsche Bank trader who was working on setting up a SPAC called Digital World Acquisition Corp.

Mr. Moss and Mr. Litinsky brought Mr. Trump in for meetings to sign off on a merger. In February 2021, Mr. Orlando arrived at Mar-a-Lago to speak with the former president. Mr. Trump had been playing golf with Jack Nicklaus, the golfing champion, company records show.

At another meeting, Mr. Trump led a group on a brief tour at Mar-a-Lago, recounting a zoning fight he had with local officials in Florida, according to a video reviewed by The Times.

Mr. Trump, who occasionally met Trump Media’s investors, leaned heavily on his oldest son, Donald Jr., to represent his interests, according to company records and two people familiar with the talks.

But in the end, the elder Mr. Trump was the “ultimate decision maker” on the SPAC deal, Mr. Litinsky testified.

Yet as negotiations unfolded, Mr. Trump considered abandoning Trump Media, according to a daily log of the company’s activities maintained by a former executive. He held talks with a rival start-up called Gettr, a conservative social media platform led by a former campaign adviser, Jason Miller.

In September 2021, Mr. Litinsky and Mr. Moss persuaded Mr. Trump to sign a licensing deal committing him to Trump Media. Under the terms, Mr. Trump would have to post messages on Truth Social before publishing them on any other platform. Mr. Trump didn’t get additional money from the contract, but it included provisions allowing him to abandon his commitments if the merger took too long to close.

Some Digital World board members were uneasy about the merger with Trump Media. On a call in October 2021, a board member, Lee Jacobson, complained that Trump Media was taking a “cowboy approach,” with financial projections that did not add up, according to a recording filed in court.

Mr. Orlando quelled the dissent, insisting that the deal was a “once-in-a-lifetime opportunity.”

A legal cloud

On the morning of Oct. 20, 2021, the merger paperwork between Trump Media and Digital World was ready for a signing ceremony at Mar-a-Lago. Then Mr. Trump got a call.

On the other end was Mr. Miller, who ran Gettr. Mr. Miller again wanted Mr. Trump to join his app, Mr. Litinsky testified in April. Mr. Trump seemed undecided about what to do and summoned Mr. Litinsky to his Mar-a-Lago office, asking him to pitch the rationale for the merger with Digital World. Mr. Litinsky said he was worried the former president would abandon the deal.

Mr. Trump ultimately did not join Gettr. Later that day, he and Mr. Orlando signed the merger agreement during a meeting at Mar-a-Lago..

Trump Media’s next step was to release Truth Social, which officially debuted on Feb. 21, 2022. “Because the president wanted a Ferrari, they built him a Ferrari,” Lori Heyer-Bednar, Trump Media’s chief legal officer, said at the time. But the site was initially plagued with glitches, prompting complaints.

Mr. Trump’s account quickly published its first post, vowing that he would be an active user. Mr. Trump did not write the message or post it; an executive at Trump Media had, according to a video reviewed by The Times.

Legal hurdles soon arose that delayed the regulatory approval for the merger. In late 2021, the S.E.C. opened an investigation into the merger, while prosecutors prepared separate insider-trading charges against a group of early Digital World investors. (No one from Trump Media was charged with wrongdoing). Trump Media’s public debut couldn’t move forward until those legal issues were resolved.

With the deal hanging in the balance, Mr. Trump moved to strengthen his hold over Trump Media. In late 2021 and early 2022, he asked Mr. Litinsky to give company shares to his wife, Melania, according to court records and a person with knowledge of the matter.

Mr. Litinsky refused. In the spring of 2022, Mr. Trump had him ousted, according to a lawsuit Mr. Litinksy and Mr. Moss later filed against Trump Media. Mr. Moss left a few months later. They were replaced by Devin Nunes, a former Republican congressman, who became Trump Media’s chief executive. Mr. Trump’s title changed to chairman and his son Donald Jr. joined the board.

By then, Mr. Trump had become more active on Truth Social, where he now has seven million followers. He posted frequently about prosecutors and political opponents, insisting that the 2020 presidential election was stolen from him.

But Trump Media was struggling to stay afloat. In regulatory filings, the company warned that it might go out of business if the merger wasn’t approved soon.

Last July, Digital World agreed to pay $18 million to the S.E.C. to settle charges that it had misled investors about the deal with Trump Media. The settlement lifted a legal cloud. Mr. Trump received a new class of shares that gave him majority voting power over the company, and Trump Media recommitted to the merger.

On Feb. 14, the S.E.C. approved the merger agreement. The company’s path to the stock market was back on.

‘People can’t stop us’

At the Mar-a-Lago cocktail party last month, Mr. Trump thanked some early Trump Media investors and exchanged pleasantries with the actor Jon Voight, a longtime supporter. Addressing the crowd, which included several conservative influencers, Mr. Trump declared that his app would be bigger than Twitter, now known as X.

“All I know is I get my voice out and people can’t stop us,” he said.

Whatever reservations Mr. Trump had about Trump Media appeared to have melted away. On March 23, a day after Digital World shareholders approved the merger, Mr. Trump posted a short message on his app: “I love Truth Social.”

When the company started trading publicly on March 26, it surged 32 percent over its first two days, closing at around $66.

After an infusion of new shares from the merger, Mr. Trump’s 90 percent stake in Trump Media dropped to around 65 percent. But he remains the single biggest shareholder with about 115 million shares — including 36 million that he received last month as a kind of bonus for the stock trading so well.

Mr. Trump also stepped back from being an officer or director of the company. He didn’t explain why, but Trump Media’s code of ethics says employees and directors engaging in “political activities are expected to do so as private citizens.”

The company’s future is not assured. While it has outperformed other right-wing apps, Truth Social had just one million unique visitors in April, a small fraction of X’s traffic, according to Similarweb, an internet tracker. Its revenue comes solely from ads, including ones for patriot-themed apparel and Trump paraphernalia. The company’s $328 million loss in the first quarter, which it reported on Monday, was affected by merger-related costs.

In September, Mr. Trump can start selling Trump Media’s shares or use them as collateral for loans. If he sells on the open market, investors could take it as a negative sign and dump their stock, hurting the share price. To avoid that, Mr. Trump could try to negotiate a private sale, cashing in on some of his shares without causing a market panic.

“There would have to be a big discount,” Mr. Jagolinzer, the accounting professor, said. “The red flags are just so glaring.”

Kitty Bennett contributed research.