Sources say he wanted to stay through some of the restructuring process    



From DailyTech:

A new report from All Things D said that interviews with sources close to Ballmer and Microsoft revealed that the retirement was planned, but wasn't supposed to happen so soon. Sources said that Ballmer had hoped to stay through at least some of the restructuring that he was planning.

In Ballmer's letter of departure, he said: “My original thoughts on timing would have had my retirement happen in the middle of our transformation to a devices and services company focused on empowering customers in the activities they value most.”

  Microsoft's Steve Ballmer Reportedly Didn't Plan to Retire So Soon