Earlier quoted context omitted.
Microsoft actually had a winning formula. Make cheap phones that work alright. And they were getting market share with later wp7 and throughout wp8. Between wp8 and WM10, they merged the phone team with the regular OS team, and eliminated (or at least gutted) their QA teams, and they decided to target the high end market only . There were no low spec WM10 phones, and there hadn't been many high end buyers anyway, so…
Yeah, Microsoft had an exceptional OS that was competitive to iOS (and much better than Android) on its foundations and APIs. It had everything needed to succeed and get a big chunk of the market, except for a clear leadership. Now, here we are, with extremely powerful Android phones that do little because they don't have a solid software foundation with which to build good software, an iOS has all the high-quality s…
From my vantage point, Google did everything it could to kill off Windows phone. There was the big spat over YouTube, where Google wouldn't write a native YouTube client and banned Microsoft's. Google bought SoftCard (I think?) and subsequently killed off NFC payments for Windows phones. When they bought Waze, they ceased all development for Windows mobile, allowing that application to atrophy.
There were certainly a lot of other reasons Windows mobile had difficulty. Not the least of which is developers didn't want to have to manage apps for yet another platform. It looked to me like Microsoft was making good strides there, nonetheless, with some nice tooling. I don't use more than ten apps with any regularity and there were solutions for each of them on Windows mobile, at least.
But, rather than make its apps available everywhere its users were, Google used its market position to starve a competitor. And it wasn't merely a case of deciding not to build apps for it. They took active actions to try to kill off Windows mobile before it had a chance to grow. I see no reason to believe they wouldn't do it with any other new entry. We're just stuck with a duopoly now.