Washington, ranked #2 after the regular season, declined the option to play BYU. They chose to play Oklahoma instead for more money. They got their money, but not the championship. They should have played BYU instead, but they didn't. Then at the beginning of the 1985 season BYU beat Washington 31-3.
Baylor coach Grant Teaff, who played both BYU and Oklahoma that year, said: "We played both of them, lucky me, and I think BYU is better. We felt we had a chance against Oklahoma (ranked #2 before its bowl game against #4 Washington), but against BYU all I wanted to do was get the game over with and get out of there."
Furthermore, BYU received the number-one ranking in ALL 4 NCAA sanctioned polls AP, Coaches, NFF and FWAA. Thus making BYU one of only 19 FBS programs which have been deemed "Unanimous National Champions".
And one more point, a bunch of BYU players on that team made it to the NFL.