Should they have known FTX was about to fail? Maybe, but so should a lot of other people who should have definitely known better. So, it’s hard to fault them for that.
In several cases they have received the money, but now feel like it is not ok (morally, legally, or both) to spend it.
Still, while victims of his fraud, they are certainly lower in standing than almost everyone else.
This is not an excuse for assuaging due diligence. And to be frank, the guy looked shifty. Even worse, a cursory look at his company would have told you he was shuffling billions of dollars in investments and user deposits without a board of directors. If it quacks like a duck...
It would do a lot of people well to assume that anybody portrayed as a wünderkind or super genius in the media is anything but and cautiously invest their time, money, and attention in them accordingly.