You probably want to read the reply above yours, or the FAQ it links. The announcement from Brendan was that he had chosen to resign. No evidence has been presented that he was fired or in any way pressured by the board to leave; in fact, everybody in the know who's commented publicly says it was the other way around (and always was -- it really looks like he never wanted to be CEO but was talked into it, then wanted to resign and others tried to talk him into staying).