Since 1980 BYU has had 38 chances to beat a P5 (or equivalent) team in consecutive games, but only 5 times has BYU won both games.
2019 Tennessee USC
2016 Michigan St and Mississippi St
2008 Washington UCLA
1990 Miami Washington St
1984 Pittsburgh Baylor
Kalani has 2 of the 5 back to back wins and the only one where both opponents finished with a winning record.