I think the Utah game broke them somehow. I think that even though BYU won the Utah game, the toxic behavior of both Harlan and Whittingham, along with the fans, affected some (or most?) of the players so negatively that it left them second guessing themselves. As if to say, "They're right, the ONLY reason Utah lost is because the refs got it wrong". And I think that mentality carried over into last night's game.
It's either that or they just ran out of psychological and emotional fuel.