I posted earlier about my Seattle -4.5 pick because elite defenses typically overperform the spread in Super Bowls.
I documented a bunch of them in the post: #1426273 but I never really articulated a plausible reason why that should be the case.
IOW, if you notice elite defenses tend to cover in Super Bowls, and you have no mechanism to explain it, maybe it's just dumb luck things turned out that way.
But here's a plausible explanation IMO:
The Super Bowl is arguably the most scrutinized sporting event in the world. Teams get two full weeks off, and tons of hype builds. Players are always more nervous in the biggest games, and performance tends to suffer somewhat -- think it was Tom Brady who said that, but maybe it was someone else. But whoever it was said the clutch players are those who can maintain closer to their usual calm when everyone else is feeling the pressure in these huge games.
Offense is about timing. The QB has to time the ball to meet the receiver. Defense is about disrupting timing. Get heat on the QB, he throws to early. Jam the WR, his route is thrown off. If you're facing a top defense that throws off your timing, it's very hard to adjust and be poised under pressure. Basically, the higher the stakes, the higher the nerves and that favors the disruptors over the timers.
On the other hand, how often does a career choke artist win a championship?
I have the same base case as you, but I also won't be at all surprised if Darnold has 5 turnovers and takes 8 sacks.
Darnold definitely choked last year in his two big games against the Lions and in the playoffs, but he didn't choke against the Rams this year. And the Pats defense is way worse than the Rams.
True, but your thesis here is that the pressure of the Super Bowl is qualitatively different.
What outcome would surprise you the most?
More pressure, but it doesn't seem like it benefits average defenses -- not like we haven't had a lot of overs come in. It's only when the defense can make you rush more than usual that it seems to have an outsized effect. And maybe that's not even the explanation, just that elite defenses have really been the difference almost every time one is in a Super Bowl. There are a couple exceptions: 2008 Steelers over the Cardinals (defense got lit up even though it was elite by most metrics) and the 49ers defense that lost to Mahomes, but it was dominating for 3.5 quarters.