I knew football fans were stupid, but this is just reaching unfathomable levels of stupidity.
QB is an extremely important position, and Brady was extremely valuable. Bill Belichick is an extremely good defensive coach who was ahead of the game for a lot of years with regards to team structure and personnel philosophy.
Almost every single great QB got their Super Bowl wins in the years their defenses peaked. Aaron Rodgers, Russell Wilson, Peyton Manning, Drew Brees, Ben Roethlisberger, even guys like Stafford and Eli Manning. Seriously, look into it -- literally every single one won when they had the best defense of their career, because it takes both sides of the ball. (INCLUDING THE GIANTS TWICE WHEN BELICHICK WAS THEIR D-COORD).
Brady and Belichick won tons of them because Brady made the offense good and Belichick made the defense good, as well as being a good gameplanner, in-game decision maker, attention to detail, and getting a lot out of players that didn't have the highest natural talent.
There is really no need to make it more complicated than that. Belichick does not seem to have an edge over the competition in GM decisions anymore. And he's always been a defensive coach. So their team sucking because the offense sucks means Belichick is not a great offensive coach which is not new information, he is a defensive Goat.
This would actually be pretty interesting, because anyone who's followed salary cap sports knows that winning eventually ruins the team. The Pats' dynasty was so unbelievable because Belichick the GM navigated constant contract bloat and player loss that inevitably occurs even winning ONCE, let alone 16 straight division titles or whatever. They basically had bad draft position and FA flight for two decades.
So that finally caught up to them the season before Brady left. Brady hops to a stacked team, but Belichick stays in the barren team. For a true comp here we'd need Belichick to go coach a team that has essentially everything in place but a HC/DC.