A while ago some anon said Phil had an injury to his skull which hadn't healed properly. That could partly be it, but Phil's problems go deeper than that. He's just unstable and far too much of an egomaniacal mark to allow for any inner reflection or personal growth. I troll Philfags on here (because it's easy and funny) but I do think Phil has good things he could offer to AEW. But Phil is his own worst enemy and looks for slights where there are none. He's a 00's teenage who never matured.
His return has been the worst thing for him. UFC exposed him badly, but I would argue his wrestling return has been worse. Once upon a time, Phil had this mystic of the underdog, the little guy standing against the corrupt system. There was a natural romanticism to his plight and character which resonated with fans and people - not just internet smarks, but with people who felt the system didn't make sense, or they felt they were punished for being non-conforming. This was helped by the fact Phil was a decent orator and could get people invested in his story, which helped people connect with him - you'll often hear Punk's fans claim he makes them "feel". For the longest time, fans swore that it was WWE who were the problem and that they never let CM Punk be everything he could. Had Phil remained retired, his fans could continue to hold to the memory of CM Punk, the folklore of CM Punk. He would have remained an excellent topic for fantasy bookings and what-ifs.
The problem is... Phil's return has exposed him as a complete and utter fraud. The second he gets a little stroke, he goes mad with power and becomes every bit as bad as Shawn, Hogan, and Paul. His entire brand is built on a complete pack of lies and he very much operates on a "rule for thee, not for me". He doesn't care about helping the company or the little guy, he cares about himself. Phil has a deep sense of entitlement and retarded enabler (TK) who allows it to flourish.