He had a good run with Bronco's team (laden with NFL talent) and was mediocre or worse from then until 2020.
Props to Sitake for playing when every other team in the time zone wasn't, and this year's team was fun, but there should be a giant asterisk next to this season. No one really knows just how good 2020 BYU was because they played an absolute cupcake schedule and lost their toughest game of the year - which incidentally was against a Sunbelt team.
I absolutely think Grimes was the culture shift that pulled BYU from the brink and got them back on the right track, but some people seem to have shorter memories.