I do think it's interesting that in two seasons of addressing "hot-button" issues, Apple had no concerns; but drew the line at AI and China. I really wonder what it was he was going to say that made Apple take such a hard stance.
Jon Stewart hosted The Daily Show for so long, I'd honestly be surprised if he ever needed to work again. To me, this means he only started the show because he really wanted to; and as such he can walk away pretty easily. I'm sure Apple knew that as well, so this must've been VERY important to them...