In 2018 and 2019 alone BYU beat 3 P5 teams that finished their seasons with 8 wins. And 2 of those wins came on the road.
Boise's last such win came in 2016 when they beat an 8-5 Wazzu team at home.
And of course BYU has now won 2 in a row between the 2 schools, including winning in 2019 with a 3rd string QB, and completely demolishing Boise last year on the Smurf Turf.
Boise has been racking lots of wins against very soft MWC schedules, and almost never playing P5 opponents in back to back weeks. While BYU is playing 3 or 4 P5's in September.