When he hired Rob, I remember thinking that it wasnt a move made by a coach trying to get better. It was a move by a coach that was trying To help someone out.
And it makes sense with Rex. People love him, but dont respect him. Players, fans, coaches. He garners no respect because all he does is talk, and sooner or later, you get exposed. He was exposed with the Jets, but was good enough to sell himself one more time (and Buffalo was vulnerable/gullible enough to buy in).