- There were multiple manufacturers.
- Despite of MS' bad reputation, the platform was surprisingly open and flexible. Not as much as Android, but certainly more than iOS.
- UI-wise, it was on par with the two big players. I would argue it was even better, at least more innovative.
Unfortunately, it failed due to devs ignoring it (especially large players), and probably MS' notorious schizophrenic behavior resulting in constant zig-zag courses.