The biggest thing for me is Tom's age defiance. It won't last forever (obviously), but you can't really blame BB for checking out when the guy was heading into his age 43 season. Correct me if I am wrong, but I think Brady played most of 2019 with an elbow injury. Plus, just like Brady knew what the Pats had coming back and what Tampa had, BB knew this as well and figured it's probably best to spend 2020-2021 finding a new QB while he rebuilt the rest of the team. This doesn't have to be a zero sum ordeal. Both Brady and Belichick can come out winners from this.
How many 44 year olds put up MVP caliber seasons? Brady and BB can both be geniuses. How much easier is it for Brady to absorb hits when he's playing half of his games in Florida? Or to rehab injuries? Brady saw an opportunity and seized it. Belichick winning 10 games after all the success of the past is still a really good feat. They are both football gods.