Steven Sinofsky has a good Twitter thread about this [1]. He's one of the few people actually qualified to talk about managing platforms and operating systems at Apple's scale.
Someone should do this poor guy a favor and set him up with a blog. Twitter is only slightly worse for writing essays than "yo" (yes, it exists; no, I have no idea whether it's a joke).
Too many downloads for a joke... Maybe drug dealers use it?
The person in charge of Windows Phone then was Terry Myerson, who had an entirely different reporting chain to Steve Ballmer from Sinofsky's. Myerson was later promoted to run R&D for all Microsoft operating systems in early 2014. (Yes, that means he was also the person responsible for killing Windows on phones most recently, at least for now.)
The death of XNA also didn't happen under Sinofsky's watch. XNA came out of the Xbox division and was abandoned by the same division, before it was combined with Windows under Myerson. If anything, Myerson kept XNA alive longer by making sure it was still supported on WP8.0 and WP8.1 when he ran Windows Phone, and by ensuring that Windows continued to fund MonoGame as an open-source successor/replacement for XNA.