It's a popular opinion around here that he hires his buddies.
I think he's just so inexperienced that he doesn't have much of a coaching circle to look at or lean on. His first HC gig lasted 2 years with 1 staff, and he brought them along to Texas. He's never fired an assistant, but look at his lack of experience. 2 years at first stop and in his 3rd year here.
And who does he have to lean on, "mentors" and whatnot? Urban would probably be the #1 guy to call, you know, the guy you worked for who is the best college coach in the past half century not named Saban. He was actually asked the question about mentors, his reply? "Well, there Mack, Greg, Larry Fedora, and the wife. The circle is extremely small".
I see the real problem is he has no idea who he should hire, he doesn't really know that many coaches, and he doesn't have anyone competent he can ask. In other words, he is completely unprepared for the job. Being a good playcaller and OC does not translate to being a good HC. Job #1 for a HC is hiring and maintaining great assistants.