That wouldn't be obvious at all to me; the lowest-risk investment in my country (federal government bonds) is currently offering over 13% interest (https://www.tesourodireto.com.br/titulos/precos-e-taxas.htm).
FTX was paying well above the risk free rate (currently 3.25-3.5%, it’s been climbing since January 2022), implying they were taking risk to earn the yield they were paying.
To guarantee an 8% payback in crypto is a completely different game, and there's a significant downside for someone taking the deal. The expected return rate is always going to be negative on a proposition like that.