Matt Levine has speculated that a bunch of the money was lost via market-making with insufficient controls (margin enforcement etc.). For example, as reported

Matt Levine has speculated that a bunch of the money was lost via market-making with insufficient controls (margin enforcement etc.). For example, as reported by the Financial Times (via Levine's Dec. 5 newsletter, "Crypto had a Credit Bubble"): [begin quote] In April 2021, a crypto token called MobileCoin — used for payments in the privacy-focused messaging app Signal — suddenly spiked in price from about $6 to almost $70, before crashing back down again almost as quickly. The wild moves came after a trader on FTX had built an unusually large position in the little-known token. Two people familiar with the matter said that when the price rose, the trader used the position to borrow against it on FTX, potentially a scheme to extract dollars from the exchange. Alameda was forced to step in and assume the trader’s position to protect FTX. The trading company’s loss on this deal was at least in the hundreds of millions of dollars, the people said, and as high as $1bn, according to one of the people, wiping out a large share of Alameda’s 2021 trading profits. [end quote] ...So whomever was on the other side of positions like that. Savvy outsider or well-informed insider? Who knows! Maybe it can be reclaimed, or maybe it's long dispersed down a chain of dozens of crypto exchanges, tumblers, offshore fiat accounts, and so forth. I expect we'll learn a lot more over the next few weeks as the federal case ramps up and the bankruptcy executor delivers more findings.