That's not actually completely true. As I understand it, the NTSB investigates crashes, and the FAA does permitting and enforcement of safety standards. They're two separate agencies specifically so that the crash investigators won't need to hold back, if there was something in the safety standards or permitting that was a factor in the crash, and needs to be changed going forward.
Of course, that's exactly the kind of corruption-resistant forward thinking that Trump hates, so he's probably going to have Elon Musk's new girlfriend take over both of them and have them both run as a single agency going forward. If they still exist at all. It might just be the girlfriend getting ChatGPT to write investigations and safety standards both.