It starts with nearly everyone associated with that program, athletic department, school, and especially the fans completely bought into and drunk the Pac12 kool-aid, which that by association, they viewed themselves as simply better than any school not in the Pac12, B1G or SEC. That continued with the attitude the Pac12 was consistently on par with both the B1G and SEC, which for the most part, did not come anywhere close to representing reality.
And many of them, including those in their athletic department, loved rubbing that in BYU's face each and every chance they got. In short, acceptance into the Pac12 and its privileges deluded them into thinking they were superior to BYU in nearly every way. The Pac12 was not the elite conference the Utes deluded themselves into thinking it was. Sure, it had it's moments, and it had its regular stars (i.e. Oregon), but compared to the B1G and the SEC, it was not even close. But that didn't stop the adoption of the illusion--and most importantly, the self-identity of superiority.
And I think that's where the problem exists--that non-reality of their sense of superiority. Since the implosion of the Pac12, they have been arrogant about their value in the sporting world, believing that they so much better than the Big XII, that they were going to run the table in the Big XII, and that it's just a matter of time before the B1G comes calling. The problem, of course, is reality. When you tell yourself lies and half truths so long, you start to believe them, but there is always a reckoning with truth. They had had enough signs of this in the last several years of the Pac12, but they couldn't/wouldn't see it--even though much of college sports saw it.
And now, both the Big XII and BYU are exposing the truth and the fraud of the UofU, and the fact that their house of cards is starting to publicly crumble is causing it hard for their fans and athletic department to deal with their new reality. They need to be dominant over the Big XII (and BYU) to show their value to the B1G or the SEC, and they are being exposed, and are not handling it well. This was a problem of their own making, and now the truth is out.