Yeah, people keep on missing the point saying "which cares if Bill was mean, it helped them win".
It was more than just being "mean", there was some legitimate resentment that Brady sensed and felt from Bill that went beyond regular hardass coaching. Belichick definitely started to target Brady, and there's reason why Welker and Moss even said that themselves.
Belichick was legitimately targeting Brady.
I figured 02 and 03 did lay the foundation subconsciously, because of how they won.
That 03 defense was one of the best of that decade, meanwhile the offense was 16th in scoring I believe. And in 2002, when their defense was worse, they missed the playoffs. So I wonder if Belichick still secretly viewed Brady as just being that 6th round pick who ran the system well but wasn't that physically talented and ultimately still benefitted from his defenses. 02 and 03 could have created that view in the back of his mind.
It would explain why he eventually stopped talking to Tom after spygate (MVP perfect season), and especially the credit he was getting by 2016 when Brady was annointed the GOAT. Belichick deep down felt that he made Brady, and was eager to push him (hence his surprising adulation of Garopollo).
That's my rational for it. It also align with the recent Wickersham quote attributed to Brady that stated Belichick "didn't know what he was missing"
I'm curious, why do you think he started to change after spygate?