Taysom and Williams returned (whether the coach was Sitake or Bronco). Had they not returned, the team wouldn't have been as good as they were. Also, Bronco's program was taylored for the go fast, go hard, go fast again offense — which generally worked. Part of the drop was NOT having depth taylored to Sitake's schemes.
Bronco was good for BYU. I think that had he stuck around one more year things may have been a little better in 2016. Also, with him at the helm 2017's disaster season probably wouldn't have happened to the degree that it did (probably 6-7 wins) — he did lose to a 3 win Missouri team and a 2 win UVA team, so we'll never know. People need to stop thinking of Bronco as the best BYU could do (fantastic?). He did well and he also made big mistakes. He also chose to leave, so let him go.
Sitake is also learning on the job. He struggled in his second year (probably because of the success that he had in his first). He'll continue to grow as an HC.... but, if he doesn't, he won't be at BYU long. I hope he succeeds. Holmoe is pretty much saying, "We're going with Sitake and he has my confidence.... for now". Don't read too much into the article.