Windows phones failed because it was a mediocre product, delivered very late by an inept company that had - in fact still has - no clue when it comes to mobile devices. "Hey, lets put desktop Windows on a mobile device". Yeah, that's a GREAT plan.
I can't wait to turn on my Windows 10 powered mobile device and have it immediately start downloading updates, rendering it useless for 10 minutes. Then it needs rebooted to finish installing. Then it has 85 processes and 1,523 threads running when I am doing nothing on it. Then when I put it down for 15 minutes, SVCHOST and/or TrustedInstaller and/or Windows Defender cranks up and uses 50-75% CPU, doing all kinds of S just because I am doing nothing. There goes the battery.
MS desperately needs a real mobile OS. Windows 10 ain't it.