There’s several reasons why being head coach at Utah is better than the nba. He will make at least as much, and probably significantly more, in his first contract than a hypothetical NBA head coaching position.
In the NBA his first HC job would more than likely be a a very bad team, so the player attrition would be worse than college recruiting. Unless you get lucky and your first job is with the Nets.
Recruiting is mainly done by your assistants. Alex would close.
He will get a lot more time at Utah than in the NBA to make the utes a winner. Example 1 is Boylen in Chicago.
Even if he fails at Utah an assistant position in the NBA will always be waiting for him, with $10mm+ in the bank.
And finally, if he wins at Utah, goes to the tournament 4/5 years, gets to the Sweet 16 a couple times, and hopefully further once or twice he’s set for 10+ years. Win a national championship and he’ll have a statue at his alma mater.