After nearly four decades, legendary short seller Jim Chanos is shutting down the hedge funds he manages that wager against companies he believes are overpriced or fraudulent. His firm, Chanos & Co., which he founded as Kynikos Associates in 1985, will stop taking new investments and will return most of the cash his investors have left by Dec. 31, the Wall Street Journal reported on Friday. Chanos, a frequent presence on television and the founder of the social media platform X is stepping down because “the marketplace for what I do has changed,” he said.

A long bull market and low interest rates have dampened demand for bearish strategies, making it difficult to make money, Chanos said. His firm managed about $6 billion in 2008, but that figure has dwindled as the markets have rebounded and Chanos’s bets have been wrong.

Raised in Milwaukee and graduated from Yale, Chanos is a master at picking out companies with questionable financials. He made his name by spotting issues in Enron Corp.’s filings two decades ago and, more recently, took prominent positions against Tesla Inc. He has also warned of a coming financial reckoning in China, where he believes companies are running up debt and hiding the impact from their shareholders.

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He has a reputation for being an outspoken critic of business elites. He said a New York Times report that White House officials held private briefings on the coronavirus pandemic’s severity while downplaying it to the public crystallized a view among some in the investment sector that the game is rigged.

At the same time, he has been trying to convince people that he is not a hysterical doomsayer. He says he advises preventing people from being caught off guard by the next recession or financial meltdown.

On a recent afternoon, he sat in a leather chair at a table in his office. A large whiteboard covered one wall with rows of scribbled notes and financial charts. Bookshelves lining the other wall are filled with titles on financial doom and bubbles.

Today, he planned to raise $200 million for a fund that bets against real estate investment trusts that own data centers. He expects the REITs to be disrupted by cloud computing from Amazon, Alphabet Inc.’s Google, and Microsoft Corp., which have already pushed most other technology companies to adapt their business models. The fund is his most prominent short position. He has also taken a bearish stance on construction and engineering companies building China’s massive infrastructure. And he has a bet against art dealers, including Sotheby’s. He believes the fad for high-end art is overheated. It is a longshot that his fund will make significant gains shortly, but he’s optimistic if it avoids significant losses. “Winning is really about not losing,” he said. “And if you can do that over time, that’s really what counts.” — By CNBC’s Yun Li.