I'm not necessarily saying I feel this way (though I do to some extent), but Bronco's achievements (in any domain of his coaching or the team) will continue to be undervalued because he is so terrible against the team on the schedule we care most about beating.
A lot of people in Columbus absolutely adored and almost worshiped Jim Tressell while at Ohio State even though he lost some big games. Why? The man OWNED Michigan.
If Bronco had simply won the games in which he was favored against Utah, everything he does would be seen in a much more positive light.