The Bears don't have the line and offensive weapons to compete for a SB even with Brady. Maybe in 2018 with that defense but not the defense that played in 2020. With a QB who basically knows every defensive play call and gets the ball out in a flash, maybe the Bears OL wouldn't be so shitty. He does a lot of the work for them. His OL is almost never unaware of a pass rusher or where the general pressure is gonna come from. And with a QB that rarely turns the ball over, constantly moves the chains, and gets the ball in the endzone frequently, then the defense gets a lot more rest as well. The defense plays with a lead more often, the DC can be a little more aggressive and not have to play the bend but don't break style as much, which tends to lead to prolonged drives and exhaustion as the game is winding down.