He Built a $10 Billion Investment Firm. It Fell Apart in Days.

Banks were eager to do business with Bill Hwang and his Archegos Capital Management — until he ran out of money.

Until recently, Bill Hwang sat atop one of the biggest — and perhaps least known — fortunes on Wall Street. Then his luck ran out. Mr. Hwang, a 57-year-old veteran investor, managed $10 billion through his private investment firm, Archegos Capital Management. He borrowed billions of dollars from Wall Street banks to build enormous positions in a few American and Chinese stocks. By mid-March, Mr. Hwang was the financial force behind $20 billion in shares of ViacomCBS, effectively making him the media company’s single largest institutional shareholder. But few knew about his total exposure, since the shares were mostly held through complex financial instruments, called derivatives, created by the banks. That changed in late March, after shares of ViacomCBS fell precipitously and the lenders demanded their money. When Archegos couldn’t pay, they seized its assets and sold them off, leading to one of the biggest implosions of an investment firm since the 2008 financial crisis.