That was Windows RT and it was a massive mistake ... Win32 and Office are Microsoft, everything else loses them money and focus. Getting into phones was their biggest mistake, getting into consoles their second biggest. Ditching Windows RT and just leveraging their win32 advantage on tablets was a great decision.
The only thing XAML has going for it is it's security model and the appstore, for the rest it's useless and slow ... win32 needs that security model as well, Microsoft is sorta kinda giving it with Centennial but it's essentially deprecated before it's even introduced. They only present it as a transitional method, not as what it should be. The standard way of developing store apps using their most powerful and useful API.