Pre-announcing that they were leaving all Winphone 7 customers behind for Winphone 8 meant that every retailer/distributor was left with unsellable stock (because they hadn't gained enough traction to sell out initial shipments).
If this was because Nokia made bad/cheap phones that were un-upgradeable or MS being arrogant isn't something I'm remembering anymore but the end-result was pissed retailers and nobody selling WP8.
All that said, WP8 did a lot better than WM10, where the WP8 phones were promised to be upgradable, and then the promise was walked back for low mem phones, and the experience was poor for qualifying phones anyway.
The final build of WM10 was actually ok on my Lumia 640; but that was way after everything was canceled and mobile Edge (this was the first non Chrome Edge) was still less usable than mobile IE, even though the renderer was better.
The really poor rollout of wm10, plus the tradition of forcing developers to make split builds to support multiple versions of windows phone/mobile made things pretty bad at the end. Calling the build for WM10 only 'universal' was icing on the cake. Android has all sorts of problems, but you can have a single APK that works on lots of versions, with some amount of new features get pushed to old OS with libraries and some new features have to be detected at runtime and use alternate flows. On the other hand, Microsoft kept making new features require using new foundation libraries that were unavailable on old phones. WinCE -> WP7 -> WP8 -> WP8.1 -> WM10 was too many step changes and developers bailed at each one. Meanwhile on the desktop, a 32-bit win32s application targeting windows 3.1 has a good chance of running on windows 11.
Also, they managed to make upgrade from wp8 to wm10 break installed apps sometimes. That wasn't great.
#notbitter
But maybe Google would have updated their WinCE apps to WP7 if Microsoft didn't make them throw all their work away.
In the US, Windows Phone tried for the "iPhone experience", which made carriers unhappy and less likely to want to sell it, which ultimately left it the case in the US at a point where only one US carrier at a time was even "exclusively" selling the latest Windows Phone hardware, and only through its dedicated retailers. It took too long for Microsoft to also realize that part of the iPhone plan in the first place was direct to consumer sales and pressuring the phone carriers to provide SIMs rather than making "exclusive" hardware deals with carriers and hoping other carriers would try to compete for buying your hardware as well.
Carriers were especially unhappy that Microsoft bought Skype at the time and tried to run it as a loss-making business to undermine carrier voice and messaging revenues.
About phone OS upgrades, remember the HTC HD2 which originally released with WM6.5 but could be upgraded to WP7 and then to WP8 through after-market community ROMs. It was also Microsoft's decision to not officially allow that.
Look at all 5 of us reminiscing here...
I remember overhearing one of the sales folk having to explain to a woman that they can't sell her the white ones, only metal ones as she preferred the chunky plastic.
However the way Microsoft has messed it all up, no one is left besides Windows team and some hardcode believers, to care about WinRT/WinUI any longer than what is only available via WinAppSDK.
In the mobile space, there was no market for just Windows Phone apps. You needed to support native Android and iOS already. WP was just another burden without a clear return.
In their desperation they started paying college students for developing apps for the platform, leading to low quality experiences.
They pushed WP hard to their channel. Many employees in MS system integrators and managed services got very cheap phones, but outside that group, just nobody bought them before in the end they started dumping them to the masses as cheapest phone in the store, but there ain't no serious market there either.
I was one of them, initially getting a Lumia as second phone even though as ex-Nokia I was kind of pissed off, developing for UAP/UWP grew on me and was much more fun than dealing with Android.
Now given how Microsoft has messed up the whole UWP, Project Reunion and WinUI/WinAppSDK I would assert there is no faith left.