That's a good reason not to fire him this year. Which they will not do.
But it doesn't apply to next year. If BYU loses to USU, that will require the team to be no better than 7-5 again, and demonstrably the third-best team in the state, with a senior quarterback, all Bronco's recruits, an upperclass-laden team, everything you could want. When Bronco took over, BYU was awful, but STILL better than USU. Losing to them next year will mean that they've passed us up. That will be enough to refuse to renew his contract, I'm predicting.
You disagree with me. That's fine. Call your own shot, but this is mine.