To say that the Patriots released Brady isn’t 100% accurate because technically he walked off his own accord. However, the circumstances that enabled his free agency were of New England’s making. In short, it all came down to money. Brady wanted a long-term contract but the Patriots weren’t prepared to hand one to their quadragenarian quarterback (via SB Nation).
The two parties failed to agree to a new contract and ultimately Brady became a free agent. But if the Patriots wanted to keep him they definitely could have. There were problems behind the scenes because of Brady’s cold relationship with Bill Belichick. Another factor was that Brady felt undervalued. The Patriots wanted to move him on and succeeded.
Mac Jones fell into the Patriots’ lap in 2021 but nobody expected him to start in Week One. It looked like former League MVP Newton was in the driving seat because of his age and experience. Neither signal-caller set the world on fire during the preseason. However, Bill Belichick had other ideas and made a stunning decision when he announced his final roster.
The Patriots released Newton and designated Jones as their starter. Newton infuriated the franchise after failing to follow health protocols (via Sporting News). His lack of professionalism combined with his patchy 2020 season made it easy. They decided to focus on the future and make Jones into potentially the next Tom Brady. It was a bold call but a very exciting one.