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'!