lifestyle choices. Young is on the fast track to get a shot as a NBA head coach. As we saw with Pope, 99% of coaches aspire to reach that level.
Coming to BYU is kind of a step down. You might see somebody go to a blue blood (like Kentucky) in that situation, but not BYU.
So if that does happen, I see a person that probably values some other things than NBA greatness. Which is totally fine by me as long as you still bring fire to the job.