FTX declared bankruptcy in November '22. At the date they did so, any debts anyone had against them were essentially frozen and converted into dollars at the rate of that day. As FTX converts their assets into money, they will pay back all of their creditors in order of priority, with taxes coming first, then customer deposits, then normal debt, and last what remains goes to holders of the stock (leaving out a lot of nuance here).

Normally when a bank (or whatever FTX was) goes under with customer money missing, people lower in the pecking order don't really expect to see any money back, so they would be looking to offload whatever FTX owes them to anyone dumb enough to buy it, at whatever valuation it would fetch. The play is that if you are a savvy investor who knows that FTX holds an illiquid rapidly appreciating asset that might be valuable enough to pay every creditor, toxic FTX debt sold at pennies for the dollar might suddenly look very enticing.

For the private equity to make bank here, then all retail investors have to first be made whole (to the dollar valuation of whatever they held in November 22 at that time), but they are not going to see any profit. The profit goes to whoever who managed to buy debt at low valuations. If Anthropic shares appreciate enough that FTX makes every creditor whole, the rest goes to the stockholders which are mostly FTX employees and also mostly going to be in prison, which is a weird outcome.