They asked TJ if he was leaving and he said no, then left. Or so the narrative was.
I have no idea what happened just what others said.
Faber has been caught contradicting himself numerous times on Podcasts. On TUF he screamed TJ was a liar. That TJ quit the team and was not given an ultimatum(Which was what TJ said). TJ Maintains that he was given an "Either you are with us, or you are blacklisted from the Gym". Faber yelled he was lying.
And yet on Podcasts, Faber clearly points out he considered going to multiple Gyms like cheating on your wife. "This is my hot new girlfriend, so I am going to bang with her in Colorado, but I will still be around in Cali sometimes to bang you" and then points out "We can't have TJ scouting our fighters for another gym. We know TJ and he is so competitive he would be watching other fighters for weaknesses, so either he stays with us exclusively, or we can't let him train with us anymore"
Obviously TJ WAS given an ultimatum and since he did not take Faber's side of the ultimatum, he got blacklisted and told "You quit on us". Basically, if you do not do exactly what Faber says, you are a traitor. So faber screaming "That's not true, you were not given an ultimatum" on Tuf was a huge lie and in Faber's mind, you taking his ultimatum was "Quitting on the team".
They don't care that other guys from TAM also still train with Duane (Duane drastically improved the striking of all their fighters in the short time he was there, which is why 4-5 of them still go train with him in Colorado).
McGregor made Faber feel like a cuck on national TV, so Faber reacted badly.