I also think BYU's style of play has hurt attendance over last few years. Not very BYU like on the offense.
I blame attendance on...
1. Last four years of mediocre play or call it "Hyped up play" followed by let down.
2. Four straight losses to Rival including the last two embarrassing ones at home
3. Style of play. More running, interrupted tempo, problems and changes to core of offense - QB and OC
4. Cost of tickets
5. Bronco at times calling out fans (though I put this last and it has more impact due to the other items).