A lot of things. The talking heads searching for clicks will attribute every win or every loss to the QB. It’s just what they do. They’re paid to create controversy. But it takes more than the QB to make it to the big dance. You have to have a good running game. You have to have good receivers. You have to have good tight ends (this is really important for the female fans), I kid, I kid. And most importantly on the offense you have to have a really good offensive line. No QB, even the elite ones, can be consistently elite without that kind of team. Just look at how Brady, Rogers, Mahomes, Burrows and Jackson are doing. Now, look at how the Cowboys, Giants, Eagles and Vikings are doing. They’re playing well without elite QB’s.
You also have to have a better than average defense. Deficiencies in any of these areas will hamper your team just look at the elite QB’d teams I’ve mentioned.
Now look at the Bills. Middle of the pack running game and the #1 passing offense along with the #2 defense in the NFL. An elite QB like Allen, Mahomes, Rogers, Brady can overcome weaknesses in one are but they can’t overcome weaknesses in multiple ares of the team. Just can’t do it. I haven’t even touched on coaching which is another aspect of the team that must be good.
My point is that no matter how good your QB is, it takes a complete team to win a Super Bowl. Not just 1 player.