"While the decision to go seems to have technically been Ballmer’s, interviews with dozens of people inside and outside the company, including many close to the situation, indicate that he had not planned to leave this soon and especially after the recent restructuring of the company that he had intensely planned.
Instead, sources said Ballmer’s timeline had been moved up drastically — first by him and then the nine-member board, including his longtime partner and Microsoft co-founder and chairman Bill Gates — after all agreed that it was best if he left sooner than later."