It's at least *somewhat* plausible that Trump was an FBI informant on Epstein. He obviously would not volunteer any personal info out of the goodness of his heart, but if he himself was at risk of being implicated, he could offer a lot of inside info to investigators that would enable them to fully prove Epstein's guilt, in return for immunity. That would have been a deal done involving just a handful of people with complete confidentiality. Trump is fond of deals, after all. It would certainly explain his reluctance for full release of the files, because in them he would be named as an informant, not as a possible co-conspirator. (and obviously he would be a redacted name on the list) But if was revealed that he was an informant, then that begs the question of what he knew and how he knew it. Trump obviously would not want that can of worms opened.