Honestly, when his compensation quadruples (or more) if he says yes, then it suddenly becomes harder to say no.
Obviously it depends on what other offers he has (if any) and where he thinks he'd land if it doesn't work out.
He also has to ask himself if he can win the must-wins. Kalani is going to lose his job for losing to UMass, UNI, USU, Toledo, and USF. All winnable games for a good coach. If Hill thinks he can take BYU's resources and win those games, he could set himself up for success at BYU.