Since I had a few private conversations with Bricky, who by the way is a nice guy, or maybe I should say, a nicer guy than some might think on this forum, I would suggest that he left for a combination of reasons. One is as you stated, because he felt the team had been dysfunctional for some time, but was sort of on the right path by keeping Cousins around, either by accident or otherwise. The other was because he was going to follow Cousins if he was traded. It's no accident that the team he switched to was the Pelicans. Cousins was his favorite player on the team. I would guess that's true of others as well.
As to whether he would ever come back or not, I have no idea. My guess would be probably not, and that's a shame. While I didn't always agree with Bricky, I felt his arguments were always well thought out, and factually backed. I will concede that I miss the stubborn son of a gun. I wish him well. The forum is poorer by his absence.