Don Mattrick surprised everyone on Monday when he announced that he would be leaving Microsoft to become the CEO of struggling social gaming company Zynga. According to a report from Fast Company, the executive left because he was unhappy with an upcoming reorganization of the company. Earlier reports suggested that Microsoft was planning major changes to help solidify its transition from software company to devices and services company. Under the reorganization, Mattrick would oversee a newly created hardware division. He was reportedly upset that he would not be receiving a larger role at Microsoft, however, which spurred his decision to depart the company. The Xbox division will be run by Microsoft CEO Steve Ballmer for the time being, although it is believed that Microsoft Studios head Phil Spencer will eventually take over the position.