1) Whitt solidified himself as the near beer version of LaVell in the eyes of Ute fans, recruits, and the program. Sure, Scalley might grab some good recruits but he's a spec of grass in the shadow of Whitt. He has a fraction of the coaching experience and has earned a fraction of the respect KW has.
2) Whitt's departure will result in the departure of assistants and recruits. Guys who are fine playing for and coaching with KW may not feel the same about Scalley. Similarly, in this college football landscape, players will enter the transfer portal on the slightest possibility that their draft stock could be affect by managerial changes.
3) Scalley's coaching theories and style will be different from KW's. He's not going to be a rinse and repeat version of KW. I think a lot of defensive minded coaches struggle to put together an offense. He'll change the play book, start the guys he likes, and hire and fire those he doesn't like.
4) He'll have to refill his own position. BYU fans know all to well that the wrong Defensive Coordinator could be disastrous for a program.
5) Last but not least, Ute fans like him now, but if he doesn't perform like they want him to, he'll find out very quick that Ute fans will eat their own kind.
I predict a big momentum shift in favor of BYU (recruiting and wins). I predict that Utah will be at the bottom half of the B12 within two years of Scalley taking over. I do not believe Utah will get the invite to the B1G without KW. Essentially, Utah becomes Miami and falls into 20 years of irrelevance.