There was also the Senate factor. Trump had to get somebody that would be confirmed by the Senate. There were too many weak-in-the-knees types who just wouldn’t vote for a really good Attorney General. A Richard Burr for example, would never vote for somebody who would thoroughly clean out the FBI. So Trump picked a former Attorney General, “sure, he’ll get through, he got through before” they told him.
It would be fascinating to be privy to the conversations, not just the “recommendations” to Trump and to see who was giving them, but also from the side of the people recommending a pick who had backchannel conversations with their “recommendation”.
I fully get the Senate approval mechanism in play, too. It makes me despise the senior Republican “leaders” all the more thoroughly.