I think it's probably less about the money, largely about career mobility. He most likely wants to be an NFL HC.
Secondly, it's somewhat about offense/style/philosophy overall. I think CMS and his crew have a pretty tight grip on offense. Liam is essentially the new young guy coming into an old boys club of guys who like to recruit and play a certain way.
CMS, the big fella, and Eddie can recruit develop RBs/ground game, and defense pretty well. Collectively and historically, they've been lack luster when it comes to passing game skill position recruiting, development, coaching, game day execution. I keep saying it all up and down this board on similar threads discussing offense, LC, etc...Between Hartline and Levis we had no QBs sniff 25 TDs or multiple 300 yd games. We've had maybe 1 1,000 yd WR, and we have no TE involvement in the passing game.
In a passing era of football when everything favors the offense, specifically QB/passing game, that is simply unacceptable. It's the equivalent of basketball teams not having a perimeter/3pt oriented offense.
I think if CMS and MB made LC Assistant Head Coach/Head coach of offense...or something like that and totally gave him full control of everything he would quit looking for other gigs for now.