
The postgame exchange between Tom Brady and Bill Belichick was brief and dissatisfying to many. That is likely because Belichick was saving it for after the game.
A few New England Patriots reporters said after the Tampa Bay Buccaneers beat the New England Patriots 19-17 on Sunday night that Belichick made a special trip to the Tampa Bay locker room. Belichick went there for a private meeting with Brady that lasted just over 20 minutes.
Belichick and Brady planned to meet up after the game, so they coordinated this meeting beforehand.
— Jeff Howe (@jeffphowe) October 4, 2021

Brady said the conversation was private.
https://twitter.com/MikeReiss/status/1444891150100353031
According to Patriots reporter Jeff Howe, the meeting was coordinated before the game. This is not unusual. Oftentimes, well-known people who have histories will plan to meet at midfield for the cameras and keep it brief publicly. They will have plans to meet up afterwards privately. It seems like that was the case for Brady and Belichick.
Still, it probably couldn’t have killed Belichick to have given Brady a longer hug (see it here). Maybe he couldn’t hide his grumpiness after a disappointing loss for his Patriots.