It was an irresistible story. The problem was that it was not true. While the media, politicians, venture capitalists, and investment bankers lauded him as a benevolent prodigy—a Warren Buffett or J. P. Morgan for the digital age—he was secretly embezzling billions of dollars of his customers’ money and blowing it on bad trades, celebrity endorsements, and an island real-estate shopping spree to rival any drug kingpin’s.