"under Nadella concluded that it would never win the application support"
And he does believe it could win it now with UWP again on even more niche devices? And frankly UWP applications like Windows 10 Mail are notable for what they lack and how much their are clumsy to use - not for being great ones.
Microsoft is keeping on fragmenting its own platforms, and from a developer perspective if you need to write complex application Win32 is still the way to go. There is the tooling, well polished after so many years, there are the libraries, etc. UWP and newer MS UI may deliver more fashionable interfaces, but they don't add much for most professional applications, and just make UI design even more complex (not everybody has a graphic artist available), while there is far less support around in tools and libraries.
IMHO a vertical integration of devices and their OS would have made UWP applications more palatable for developers, but if you have Android there, Windows 10X here and then plain old Windows 10, with some Linux thrown in, it becomes quickly a nightmare.
IMHO Nadella hates the desktop - but once MS loses it it will lose everything.