1. Oklahoma lost their starting QB to injury. Sure, that's something that a lot of teams dealt with (including BYU), but I think that impacted Oklahoma.
2. Oklahoma was above average last year, but not great. BYU had a shot at home against them regardless.
3. Aidan Robbins and Kody Epps were back, seemingly in full health. And BYU made tweaks to their offensive line that made a significant difference against the two Oklahoma teams.