TCU, Utah, Boise State, Hawaii, No. Illinois, UCF, etc. all went to BCS bowl
games with the same or fewer resources than Bronco had. We weren't asking him to actually win a national title (although, everyone wants one). Fans just wanted him to put everything together and get us to a premiere bowl game.
He had his chance several years in a row, but failed to adequately prepare for such power houses as Boston College and a mediocre Arizona team. He lost those (and several other) heads cratchers, then badly botched the Heaps/Nelson affair, and fans became rightly frustrated.