Google had apps for Windows Mobile 6, and Microsoft chose to throw that app ecosystem away for Windows Phone 7. WP8 could run WP7 apps, but for the best experience, you needed to redo a bunch of stuff in a way that only worked for WP8. Same thing for WM10, except that this time, Microsoft called it Universal, although a Universal app didn't work on the WP8 and WP7 devices; and AFAIK, WM10 never surpassed 7 or 8 in active devices; whoops.

Also, I had heard Microsoft blocked 3rd party browsers early on, when Mozilla wanted to develop Firefox for WP, that would have been a lot nicer than mobile IE and later Edge, and probably would have run YouTube just fine.

On the dates, I see a RTM date of Nov 2015, and GA of Mar 2016 for WM10; I think the end of QA and the merger of Windows Phone with Windows was actually at the same time, Nov 2014, AFAIK. It's a bit tricky to nail it down, but I think this article, read with hindsight speaks to those changes. https://www.zdnet.com/article/microsoft-layoffs-operating-sy...

We just retired a Lumia 950 XL in my household. It's an all around better experience than Android in my experience, but there wasn't much point in continuing to push the boulder up the hill. And I liked the ability to pop in a micro SD card, which Apple doesn't support.

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.

There are some differences between Android phone, so it's difficult to judge if you don't list the right one.