BB may well be the GOAT coach, but he always got WAAAAY too much credit. No coach has even gotten half the credit Bill did for his wins as far as I know. The fact that it was even a debate between how much was Brady and Bill as the prime mover of success was silly. It was always Brady. And not just 51/49. It was 80/20. A bad coach can keep a QB from reaching his potential, but you if you are at least okay, you'll go very far.
Does anyone really think Dungy was responsible for Manning? Was McCarthy responsible for Rodgers? Was Payton responsible for Brees? Does anyone really think these players needed these coaches to be successful? Players play and coaches coach. The coach's main job is to do the obvious, get everyone pulling in the same direction and know how to manage a game.
In football in the cap era it has always been QB > GM > Coach in that order. One REALLY bad link in that chain can sink you, but if you get to pick which you want in order of best to worse, the answer is QB > GM > Coach.