I don't think anyone should be surprised with how Brady played this year. For me the big surprise was the Bucs actually solving their broken scheme, likely at the urging of Brady in concert with the offensive staff. This is what I posted in March:
Bucs run a ton of intermediate routes under Arians. What's missing is featuring the RB in the passing game, and fusion between the run and pass game (play action). Pass protection is what I'd be concerned about if I was Brady.
No question Brady would be a downgrade from Winston on the deep throws. He's also 43 and not nearly as mobile and durable. Those are the reasons why I'm not a fan of that swap.
It took until the playoffs for a Buc RB to become even serviceable in the pass game and for the scheme to make it a priority to checkdown vs the blitz rather than forcing vertical shots and 1on1s on the outside. Pass catching RB was the big weakness of the team I identified before the season and it was worse than I expected.
It wasn't until after the late bye week that the offense skewed more play action heavy, and the 1 playoff game where it didn't was the Saints game that easily could've been a loss (and 0-3 vs Saints) if Cook doesn't fumble.
Pass protection was solved with Wirfs and improved play from Smith and Cappa. But Brady also helps with his consistent drop points and quick time to throw.
One thing I got wrong was the deep ball where Brady was as good as Winston in 2019. He showed the arm strength on the Pats as recent as 2019 but wasn't that accurate. He wasn't perfect with it this season but you couldn't ask for better from a 43 year old QB on a new team in a season with no real ramp-up.
Also Jameis' mobility advantage was negated by how clinical Brady was/is in the red zone, especially with the Gronk addition. You don't need rushing TDs when you can just throw them instead.
And the biggest impact was in the locker room and in the minds of the 52 other guys playing with him.