When Microsoft (NASDAQ: msft) unveiled Windows 8 less than a month ago, Sinofsky called it "a major milestone in the evolution and the revolution of computing."
(Read More: Microsoft's Windows Unit Head, Possible CEO, Exits )
That's why Microsoft watchers were stunned that Sinofsky, a 23-year company veteran, is leaving.
According to a report from All Things D , Microsoft's co-founder and former CEO Bill Gates decided to back CEO Steve Ballmer's move to part ways with Sinofsky.
Basically, Ballmer wanted to allow for more integration within divisions of the company and involve more executives in the development of future versions of Windows OS, the report claims.
But Sinofsky was not a fan of involving other divisions in his work and had a reputation of being somewhat difficult to work with, David Hilal, director of technology research at FBR Capital Markets, told CNBC Tuesday.
"On one hand, Sinofsky was known as a great manager to get products out on time," Hilal said. But "he's known for not necessarily playing well in the sandbox and this is the time that Microsoft certainly needs to get all of its divisions working together."
Sinofsky, though, assured Microsoft employees that this wasn't the case.
"Some might notice a bit of chatter speculating about this decision or timing," he said in an email to employees. "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."
Read the full email below.
With the general availability of Windows 8/RT and Surface, I have decided it is time for me to take a step back from my responsibilities at Microsoft. I've always advocated using the break between product cycles as an opportunity to reflect and to look ahead, and that applies to me too.
After more than 23 years working on a wide range of Microsoft products, I have decided to leave the company to seek new opportunities that build on these experiences. My passion for building products is as strong as ever and I look forward focusing my energy and creativity along similar lines.
The Windows team, in partnerships across all of Microsoft and our industry, just completed products and services introducing a new era of Windows computing. It is an incredible experience to be part of a generational change in a unique product like Windows, one accomplished with an undeniable elegance. Building on Windows, Surface excels in design and utility for a new era of PCs.With the Store, Internet Explorer, Outlook.com, SkyDrive and more, each of which lead the way, this experience is connected to amazing cloud services.
It is inspiring to think of these efforts making their way into the hands of Microsofts next billion customers. We can reflect on this project as a remarkable achievement for each of us and for the team. Our work is not done, such is the world of technology, and so much more is in store for customers.
It is impossible to count the blessings I have received over my years at Microsoft. I am humbled by the professionalism and generosity of everyone I have had the good fortune to work with at this awesome company. I am beyond grateful.
I have always promised myself when the right time came for me to change course, I would be brief, unlike one of my infamous short blog posts, and strive to be less memorable than the products and teams with which I have been proudly and humbly associated. The brevity of this announcement is simply a feature.
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 readabout me, opportunity, the company or its leadership.
As Ive 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.
I am super excited for what the future holds for the team and Microsoft.
With my deepest appreciation,
Sent from Surface RT