The Matt Levine article looks at that and claims quite a lot of it is just tokens issued by FTX themselves or related trading entities. In the words of Walter Sobchak from the Big Lebowski : "Mark it zero!"
Perhaps "only" $5bn was real and much of that was from institutional investors. Not yet clear how many retail rubes have been caught up in this.
I am not a crypto expert, but from the bit I do know, it seems as if it's fairly difficult to correlate fiat with crypto.