It hasn't been even a month since the launch of Windows 8, Microsoft's most radical Windows update since 1995, and Surface RT, the software company's first ever PC, but Steven Sinofsky, the man who led the division responsible for both products, is out. The question on everyone's lips is "why?"—and conjecture is rampant.

In his farewell e-mail, Sinofsky maintained that the decision was his:

Some might notice a bit of chatter speculating about this decision or timing. I can assure you that none could be true as this was a personal and private choice that in no way reflects any speculation or theories one might read—about me, opportunity, the company or its leadership.

Such statements always lead to a certain degree of incredulity; with few exceptions (egregious violations of HR policy, in particular) departures of senior management are almost always presented as personal decisions that are mutually agreed upon, regardless of the degree of internal conflict that provoked the departure in the first place.

Nonetheless, we can't dismiss this out of hand. Leaving just after a project is completed makes sense, and switching teams or leaving the company entirely just after a product ships has some precedent within Microsoft. Jim Allchin, for example, was president of Microsoft Platform Products & Services, the (now defunct) division that was responsible for Windows client and server development. He left at the end of 2006, just after Windows Vista was completed. Similarly, Brad Silverberg, who led Windows 95's development, left that division shortly after the operating system shipped.

As for the abruptness of the departure? Sinofsky wrote:

As I've always believed in making space for new leaders as quickly as possible, this announcement is effective immediately and I will assist however needed with the transition.

The problem with this is that an abrupt departure with neither a clear explanation nor a transition plan just doesn't look very good. Microsoft's stock is sharply down today on the back of the Sinofsky news—down more than three percent at the time of writing, against an overall NASDAQ drop of a little over a quarter of a percent—and is trading at its lowest level for six months. If this really were the mutually agreed, orderly transition that the statements from Sinofsky and Microsoft CEO Steve Ballmer claim, announcing it this way was immensely irresponsible. Corporate officers have a duty to protect shareholders, and this didn't do that.

By way of comparison, Jim Allchin's departure was announced fifteen months before it actually occurred. That's not say that the Sinofsky decision was made and put into action on Monday—there's speculation by ZDNet's Mary Jo Foley that something happened between Sinofsky and Ballmer a few weeks ago. Yesterday may have simply been the earliest that Microsoft felt it was "safe" to part ways with Sinofsky to avoid damaging or overshadowing the Windows 8 launch.

As such, the widespread belief is that something a little more abrupt and a little less mutual was to blame. One thing obviously not to blame is Windows 8 or Surface. Though the critical reception to both products has been decidedly mixed, it's simply too soon to declare that they've failed (or succeeded) in the marketplace. While enterprises in particular may not rush to embrace Windows 8, it's hard to believe that Microsoft management didn't expect at least some push back—they know that Windows 8 introduces training costs that companies may very well want to avoid.

Moreover, if Windows 8 were the problem, there's no way that Julie Larson-Green would be selected to lead Windows engineering. Larson-Green was a trusted Sinofsky lieutenant who came with him to Windows from the Office team and led the development of Windows 8's controversial user interface. If Windows 8 does prove to be a failure, then it's as much on Larson-Green's head as it is Sinofsky's.

Jockeying for position

Another possible cause is a battle over the CEO position. Sinofsky was seen by some as the obvious candidate to succeed Steve Ballmer after Sinofsky's successful management of Windows 7, and Business Insider is reporting that Sinofsky resigned after Ballmer refused to give him the nod.

This narrative has a number of issues, however. Apart from anything else, the job simply isn't open at the moment. In 2008, Ballmer said that he was going to stay in the job nine or ten years, until his final child goes to college, meaning he has another five or six years at the helm. Ballmer has no reason to stand down from the position, and if he sticks to his previously announced plan, it would be too early to bless Sinofsky as his successor. Five years is more than enough time for Sinofsky to suffer a major setback (such as catastrophic Windows 8 adoption), and it's enough time for other viable CEO candidates to emerge.

In any case, the CEO job isn't Ballmer's to give. It's up to the board to appoint a new CEO. Ballmer could make recommendations, but it's not within his powers to decree that Sinofsky, or anyone else, should succeed him.

This narrative also presumes that Sinofsky even wants the job, and that he'd be suitable for it. That suitability is a big concern; Sinofsky has had some fractious relationships with the press, sometimes being downright rude, and a recent profile by Jay Greene at CNET argued that Sinofsky was a motivating factor in the decision by many other high-ranked Microsoft employees to depart the company. That's not really good enough when you're the CEO.

Feeling Blue

This leads to the most plausible reason for Sinofsky's departure: a difficulty working with others. Ballmer's e-mail announcing Sinofsky's departure praises Larson-Green's "proven ability to effectively collaborate and drive a cross company agenda" as if to emphasize the importance of collaboration and working with the entire company, not merely the Windows division.

Windows 8 may very well be the last version of Windows developed as a monolithic entity on a three-year schedule. Microsoft's future is codenamed "Blue." According to company insiders we've spoken to, this will not simply be a new version of Windows; it will be a set of coordinated, tightly linked products, released annually. In Blue, Windows development will not be handled exclusively by the Windows division. Windows 8 took some tentative steps in this direction, with the suite of Bing apps and the Xbox-branded Music and Video apps, but Blue will take this further still, with core features developed by other parts of the company.

This makes inter-departmental cooperation and collaboration more important than it has ever been.

Against this backdrop, Sinofsky's uneven relationships within the company become a substantial liability. Microsoft can't pull this off if teams are unwilling or unable to work with one another. Driving out big names, as happened with Chief Software Architect Ray Ozzie, head of Entertainment and Devices Robbie Bach, and Entertainment and Devices executive (and father of the Xbox) J Allard, isn't acceptable when the company is (finally) wanting to act like a singular entity and not a bunch of competing departments.

Compounding this, there are rumors within Microsoft that Ballmer plans a reorganization to ease this new approach to software development. New teams, new responsibilities, and perhaps even the beginning of the end of the siloed mentality and viciously defended fiefdoms that are said to define the company today. An imminent reorganization would go some way toward explaining why Sinofsky hasn't been replaced in his role: there is little value in appointing someone, just to reshuffle the deck in a month or two anyway.

Sinofsky, however, recently penned an internal blog post outlining why this collaboration doesn't require a reorganization at all. If Ballmer is dead set on reorganizing, then such a post could be seen as a direct challenge to his authority and an unwillingness to participate in the new world order. Sinofsky may also have been unhappy about whatever his new role was due to be.

Unless someone at a high level within Microsoft starts talking, it's unlikely that we'll ever know the full story of Steven Sinofsky's departure. The effects within Microsoft won't be seen immediately; even if Blue proceeds exactly as we're told it will, it's still a year out. For all the stories of difficulties working with Sinofsky, Microsoft has still lost an important employee who ran a tight, regimented ship that delivered both Windows 7 and Windows 8 on time, with none of the disarray that afflicted Windows Vista's development. Strong guidance matters, and Sinofsky provided that in abundance. It was missing before he came to the Windows division. Microsoft can't afford to let it go missing again.