In the FTX International terms of service ( https://help.ftx.com/hc/article_attachments/9719619779348/FT... ) they say that users have full title, ownership and control of digital assets. They say that the assets are the property of the user, and shall not be loaned to FTX trading, shall not be treated as they belong to FTX trading, and that users control the assets in the account.
So if they did indeed loan out customer deposits, that is just straight up criminal fraud, open and shut. This isn't like some DeFi scheme where they are working around some legal loophole or in the fine print tell you that they will probably lose your money. This is just straight up illegal under the plain vanilla theft and fraud laws of any country. This isn't even a bank run (banks at least tell you they are loaning your deposits out) -- it's a run on a U-Haul self-storage where you find out that they actually sold all the furniture in your storage unit to a pawn shop.