The thing is Marty went through brick walls to establish his Eliteness.IMO, you are. Marty's a quick study who is constantly trying to get better and we haven't seen a fully experienced version of him. Judging him by how he's been in his first two seasons is a bit premature.
I disagree with the notion that he's simply here in the interim. HuGo hired him to grow with the team. All great coaches are the actual captains of their team and Marty already fits that role to a T. His crew will go to war for him. If they need someone for better X and O's, they'll simply add someone rather than replace someone the players see as one of their own.
Elite players rarely make good coaches, but I feel MSL is the exception to the rule.
There is no reason to doubt he'll put the same efforts into his coaching career.
Hiring Grillo is a clear indication he knows he's not nearly good enough yet.