IMHO: it's driven by multiple MS Windows Teams, the following blog explains it very well:

 "... WinDiv, dissatisfied with DevDiv,..."

My personal conclusion: WinDiv created something like an 'Anti-CLR', named Windows Runtime (WinRT), but IMHO it's an architectural disaster! For example:
They extracted a confusing subset of the Win32 and COM API, see MSDN:: 

and now they call this 'reinventing windows'!