Choi, a Hong Kong native and Canadian citizen who studied accounting at the University of Waterloo, is the sole owner of a vehicle that controls 32.5% of AMTD Group. His father is also involved after a company that belongs to him acquired a majority stake in it in 2015. AMTD Group owns 50.6% of AMTD Idea, which in turn owns 88.7% of AMTD Digital.

Choi has been a fixture at annual financial technology events in Singapore in recent years. At an event co-organized by the Monetary Authority of Singapore, AMTD Group was among the biggest sponsors for three consecutive years through 2019, when Choi spoke on panels with executives including Standard Chartered Plc Chief Executive Officer Bill Winters.

Earlier this year, though, Hong Kong regulators banned Choi from the securities industry for two years for failing to disclose conflicts of interest in transactions he worked on while at UBS. He’s appealing the decision. China Minsheng Investment Group Corp., an AMTD Group investor that installed Choi as CEO, turned against him and at one point placed banners in Hong Kong’s central district denouncing him.

Separately, Hindenburg Research has blasted AMTD Group. In an April 2021 report on Ebang International Holdings Inc., a China-based crypto company, the short seller said its track record as an underwriter was “abysmal,” with 87% of its US IPOs resulting in losses.

Choi admitted in a statement last year that he’s faced challenges.

“There are those who envy and [are] jealous, and those who are cold-eyed and mockers, and malicious, there are slanderers,” he said. “However, entrepreneurs must insist that development is the last word.”

AMTD’s surge has those from Hong Kong to New York speculating about what, if anything, is behind the moves in the stock. One explanation is that only a small portion of its shares are available for trading.

“The stock is highly overvalued,” said Thomas Nip, a research analyst at Valuable Capital Ltd. in Hong Kong. “The low free float in the company’s shares means it will be easier for big shareholders to push up the stock price.”

While the recent rally in the US was reminiscent of the retail trading mania that drove up shares of companies including GameStop Corp. last year, some Reddit and Twitter users appeared baffled by the gains, denouncing claims that the sub-reddit WallStreetBets was behind the moves. At one point on Tuesday, AMTD Digital’s market value rose above $400 billion, while AMTD Idea shares surged as much as 520%.

“Given the speed of its ascent, I have a feeling this one will nosedive,” said Oktay Kavrak, director at Leverage Shares. “I hope investors take profits along the way as the inevitable crash will send HKD back to relative obscurity.”