Quarterbacks don't kill coaches. Specifically not Quarterbacks who don't cause locker room problems. You know who kills coaches? Coaches. Coaches who are too damn stupid to play to a QB's strengths, rather than trying to attack his weaknesses. Coaches who, despite all evidence to the contrary, refuse to believe that protecting a QB and...oh, I don't know...giving him a power running game...is a WISE choice. Coaches who put more value on a complete lack of chewing gum wrappers on a locker room floor than maybe giving his QB a vote of confidence. Coaches who, for whatever reason, decide to run a three receiver set...where all the receivers run 7-yard hitches. For an entire game. And then...when it doesn't work, blame everyone but themselves.
That's who kills coaches. Immeasurably dumb-*** coaches. You know what else immeasurably dumb-*** coaches kill? Fanbases and player careers.