Well Bobby might not leave anymore, but that doesn't mean that UM isn't a stepping stone program. There isn't a single FCS program that isn't a stepping stone program. With some rare exceptions, especially if you're a 60+ year old retread, all of these coaches want to advance up the ladder. It's increased money, increased prestige, it's how you get the chance to coach at a premier program.
Fwiw, NDSU's last several coaches have all moved up the ladder. The only reason nobody at UM has is because Pflugrad got fired before he wouldn't been able to, and everybody else post Hauck 1.0 hasn't been good enough to move up. So it's not that UM isn't a stepping stone, it's just that your coaches haven't been all that great lately. And I don't think calling these programs a stepping stone is an insult, it's just the reality of being an FCS program. There aren't any better places to coach in the FCS, that's without a doubt, but it's still seen as the JV league nationally.