Underhill thinks Carr will be Saints starter [mod edit: Moore-Carr meeting went well; Saints plan is to keep Carr in 2025 & figure out contract]

If you have a midtier QB, to win a superbowl, your defense better be either historic or borderline historic.
You're assuming Carr is just middle tier. Moore thinks he's better than that.

Even so, you don't have to have a "historic or borderline historic" defense to win with a Super Bowl with a middle tier QB. You just have to have a solid offense, defense, special teams and really good coaching.