2 things. First, Brady is perennially underpaid, as such he generally has a top 5 defense. Second, just because a QB got immediately paid AFTER he won as underpaid supports the opposite side of the argument you are trying to make.
Edit: To make it more clear. Maholmes immediately paid. Hasn't won since (yea, I know, yet to be seen). Goff paid...Huge mistake and Rams are in cap hell desperate to trade the future to win after that contract. Wilson paid. Defense fell apart. Team hasn't done shit since. Flacco paid...need I say more. Kapernick paid...need I say more. Eli won his first Owl on his rookie deal (6y for 54m) and his second while the impact had not hit the cap yet. He was not highly paid for either win. Brady made $25 million for his win last year...you call that highly paid for todays QB??
Your data is really supporting the other side of the argument. I'm not even sure the cap hit for Rodgers hit until after he won his and then never won another.