I think it's about connections and relationships. I'll use the Commander's staff as an example. They have two form HCs on the offensive side: Kliff (Cardinals)and Lynn (Charger, now )run game coordinator, and the QB coach is a former backup who's been on several staffs. As another poster said, the coach needs to merge their system with what the QB does well. However, in our case, I don't know how much can be done with our current QB room.