Because people will grasps at anything straws they can do demean someone and tell their own narrative to make themselves feel better. By all these guys' standards, a college career is "wasted" if you don't go undefeated, win the CFP, and get drafted #1 overall. Mario led that team to a Rose Bowl title and helped him get drafted #6 overall, and he really should have gone #3 if it weren't for poor Dolphins scouting.
It's no different than them pointing at his FIU record and looping it into his coaching ability. "hE's OnLy 62-60!" Ummm, have you seen how EVERY other coach has performed at FIU? Not great. That place is a dumpster fire. Guy performed a miracle there, by all accounts. And forget the fact Saban wanted him and mentored him. What is his record since taking over at Oregon, a P5 school? 35-13 (.729). Does he have to answer for the bad Utah losses. Sure. Every single coach has bad losses on their resume, Saban included. It happens. I think he has a much better staff here than at Oregon, so hopefully that translates as well.
People see what's coming and are in the denial stage. They are hoping beyond hope that he fails because, if he succeeds, they are all in a world of hurt.