The verdict capped one of the fastest and most spectacular falls from grace in modern corporate history. Just a year ago, Mr. Bankman-Fried was worth more than $20 billion and hailed as a rare good guy in the freewheeling crypto industry, his face plastered on billboards and magazine covers. FTX, valued at $32 billion at its peak, was one of the world’s biggest marketplaces for people to buy and sell digital coins like Bitcoin and Ether.

In a news conference outside the courthouse, Damian Williams, the top federal prosecutor in Manhattan, said Mr. Bankman-Fried had “perpetrated one of the biggest financial frauds in American history.”

“The crypto industry might be new,” he said. “But this kind of fraud, this kind of corruption, is as old as time.”

Mr. Bankman-Fried tried to dismiss FTX’s collapse as the unfortunate result of a monumental accounting error, rather than a deliberate fraud. But at his trial, prosecutors argued that he had repeatedly lied to customers, lenders and investors, using their funds to build himself up into a crypto titan.

The trial reached a climax late last month when Mr. Bankman-Fried took the stand. He insisted that he had never intended to commit crimes and had just wanted to build a successful company. But on cross-examination, Danielle Sassoon, a lead prosecutor, exposed cracks in his story, showing the contradictions between his public statements and how he behaved in private.