BYU is heavily reliant on the big play (at least in relation to most other teams)
BYU spends a higher percentage of their downs in harder-to-gain-yardage situations (mostly red zone yards are harder to come by than yards outside of the redzone)
BYU is overly reliant on turnovers and Def/ST scores for points
BYU is building big leads in the beginning and then playing a type of defense that allows easier access to success plays (aka, "Prevent")
BYU is lucky