its not brady or belichick... its not belichick or brady... it was Brady and Belichick
Belichick benefited from having Brady, a driven player who placed winning above all else...
Brady benefited from having a coach who was as driven as he was to win...
Belichick in Cleveland? That was a different era, the game was different, players were different... 5 years learning the job, what it takes to win, time spent refining his process... learning what he wanted in a player, and yes learning how to get what he wanted from the player... he tore that team down and was rebuilding it when the decision was made to move to Baltimore... who knows what would have happened if Modell kept him instead of bringing in ted marchibroda
Brady was able to succeed early on because of that insight, that coaching... He learned how to be a quarterback from Belichick... and more importantly Brady was willing to learn, and the guy aced it... He took what he learned and became the best ...
This past years success as a direct result of what Brady learned during his time in New England...
As for Bill and New Englands lack of success in 2020, all i will offer its not easy replacing a player like Brady... Harder to build a team than it is to go to a team that was able to rebuild over multiple seasons, that was lacking one or two pieces... Winston held that team back in his first year under Arians because he wasn't capable of running it property... his 30+ interceptions is direct evidence of that...