We don't know exactly yet because details haven't been released and UC has been pretty mum. The Athletic article about his practices and players constantly needing IV's and the medical staff having to intervene is pretty damning though. That's about the most we've gotten so far. On top of his entire freshman class leaving, Cumberland hating his guts, multiple upperclassmen leaving, some without even notifying the staff, and the strength coach leaving because of Brannen.
And now him and his attorney are trying to drop these little tid bits through the media to try and sow division, dragging Fickell and the football program into a situation they have no involvement in. There were rumors early on that a big catalyst to all of this was Brannen and the staff accidentally sending texts to current players that were meant for recruits. The texts were sht-talking Harvey after he decided to sit out the year. So Brannen releasing private texts with Fickell as he's headed out is no surprise. That's what I mean by showing his true colors publicly.
Sayonara John, ya scumbag.