Bill Belichick was announced as North Carolina’s next head coach on Wednesday, a shocking hire that will impact college football for years to come. But it turns out the surprise move had less to do with Belichick’s desire to join college football and more to do with his frustration at the professional level.

Part of Belichick’s turn to college programs was that he was “disgusted” with what the NFL has become, ESPN’s Seth Wickersham reported Thursday. Belichick was reportedly frustrated with NFL owners who seemed unwilling to accept his approach; Another Belichick confidant told ESPN that he was “sick of the stupidity in the league.”

As a result, Belichick viewed the higher education landscape as “more transactional and less relational,” according to ESPN. Wickersham wrote that Belichick’s decision to leave the league was “a big f*** to the NFL,” according to a confidant.

Multiple executives told Yahoo Sports’ Jori Epstein on Wednesday that Belichick knew which NFL teams with openings would have been willing to consider him and how much leeway they could give, and that he decided to do something new Try it out instead of sitting out another setting cycle.

According to Epstein, the UNC program offers Belichick a new structure to try out, where he can build a program in new and potentially revolutionary ways. Crucially, Belichick, who likes to have broad control over how he does things, doesn’t need to have owners to answer to.

The hiring of Belichick to lead the Tar Heels sparked a series of strong reactions in the sports world. Some believe the move is brilliant; others fear (or perhaps hope) that it will be a disaster. (For North Carolina, it seems worth the risk.)

Still, it’s not entirely unusual for a Super Bowl-winning coach to move on to college. Belichick will be the second person to move from the pros after Bill Walsh; In all, nine Super Bowl-winning coaches went on to coach college at some point in their careers.