Why was George fired from the Yankees?

From The Muffin Tops:

Mr. Steinbrenner is sitting at his desk on the phone with the manager at Tyler chicken who is also sitting at his desk.

Mr. Steinbrenner: (the back of his head to the camera) John Tyler? George Steinbreener here. I want to talk about George Castanza. I understand he's been dividing his time between us and you. I cannot have that.

John Tyler: (the back of his head also to the camera) Well I don't know who he is but if you want him that bad I'm not giving him up that easily.

Mr. Steinbrenner: Oh is that so. Playing a little hardball huh Jonnyboy?

John Tyler: How about this. You give me Castanza, I convert your concessions to all chicken no charge. Instead of hot dogs, chicken dogs. Instead of pretzels, chicken twists. Instead of beer, alcoholic chicken.

Mr. Steinbrenner: How do you make that alcoholic chicken?

John Tyler: Let if ferment, just like everything else.

Mr. Steinbrenner: That stuff sounds great. All right. I'll have Costanza on the next bus.

This then led to the Season 8 Finale, The Summer Of George