People still can't admit that a coach's effectiveness is never a straight line, huh?
Let's try to make this clear. Belichick's football knowledge has always been absurdly high. There is no doubt he will always be one of the most brilliant football minds in the history of the sport.
But that is not enough to make a head coach. Most importantly, you need to have good judgement. And this is where Belichick lost most of his ability to be a head coach. He started making decisions that were not based on what made for a good football team, but rather, that made his life easier.