RPGMemes

They've never really said why he left and most Critical Role communities will shut down any discussion of it. Not sure why. It's a DnD game. We've all had to deal with bad players.

The cast refuses to speak about it out of respect for Orion, and most CR communities respect that and ban any discussion or speculation as to the reason for his departure.

Orion has come out since then admitting to having a drug problem, so that (in conjunction with the extensive list you posted) seems the most likely explanation for him getting the boot.

Also of note, he made his own spinoff audio series based around tiberius and his adventures, in defiance of tiberius being canonically dead in CR. He made a kickstarter to turn it into an animated series but evidently just ran with the money and the series never materialized.