You make a good point about history. 
Standing as we are in the middle of the thing, it appears to me that when Trump terminated Comey, he unwittingly assured that the investigation will take on a life of its own, and while he can (and will) delay, deflect, lie and dissemble (as he has for the whole of his life), the investigation will  proceed inexorably to its conclusion.
Trump will have a hard time at the FBI.  He will not be able to get the pliable person he needs there; and whoever goes there will be subject to extraordinary scrutiny. No-one who works closely with Trump will escape with his or her reputation wholly intact; going forward, I think he's going to have a hard time getting quality people to work for him at all.