It’s a little bit innocent to think that SBF isn’t intelligent; he’s extremely adept at lying and manipulating. And on top of that, intelligent enough to create a large crypto exchange. It’s his morals and impulses that got him into trouble.
TBH I don't think the interviews hurt him much, and I think more than likely they are a strategy trying to reduce his culpability. The common thread among all his interviews is "I'm really sorry for being such an idiot", basically trying to play stupid to make it difficult to prove intent.