Every QB guru coach has had guys they couldn't fix that they thought they could. In this offense, with the wide splits, you need a QB with a pretty strong arm. Milton was about his only option that he could get when he was first hired. Only other QB he has recruited that we've seen play is Nico. Nico had all the physical traits you want to see in a QB. There are other things that go into recruiting as well, such as how will recruiting a certain player "due to hype" result in with recruiting other positions. If I had to guess, and its pure speculation, Nico covered the physical traits, and the make some buzz for recruiting that we needed for momentum getting started. My guess is coach thought he could develop him into a leader, and maybe misjudged his family interfering with his coaching of the kid.
Again this is all just speculation, but I dont think we've seen enough to say that coach is to blame entirely.
Sometime good parents end up with bad kids, many times the accountability falls on the student, not the teacher.