You have to understand that Windows comes from a separate division than .NET and they have no overlap. Microsoft isn't a cohesive company. .NET comes from the developer division (DevDiv) and UWP comes from the Windows division (now Server & Cloud). The Windows folks always hated .NET and the developer division has been lukewarm about UWP.

The Microsoft panel of this comic sums it up nicely: https://bonkersworld.net/organizational-charts

Microsoft care about .Net. It runs the Corporate world like Java