I was a telco product manager at the time and I can tell you right away that it wasn't developers that killed Windows Phone. This book (https://asokan.org/operation-elop/) tells part of the story, but the telcos I worked for (and competed with) definitely played a big role.
That book is new to me. I wrote https://paulhammant.com/2013/05/07/android-and-the-art-of-wa... on Google vs MSFT and phones before the book. Mine's a perspective that doesn't mention Nokia or its leadership.
I did own a Treo and loved it up to the OG iPhone - I repaired the eff out of it in the hope that something worthy would come along. I kidded myself I would write apps for it. I'd previously played with Simbian tech (and met a very bitter Simbian team dev in London one "eXtreme Tuesday Club" meetup in 2003). I had a Psion Organizer way back and Palm pilot. I thought Palm's WebOS stood a chance. I still own a Ubuntu Phone that I don't use - single script QML apps would have been the killer, but all that's passed now.