WinRT may have been buggy but the mobile OSes were not so bad. They had mobile OS releases mirroring XP, 7, 8/8.1, and 10. The problem is Microsoft made no commitment to non-secureboot hardware on non-Intel devices and all of these devices were extremely locked down and not accessible to end users. Consequently, no one cared about them. You probably didn't even know they had a mobile OS patterned after Win7, right?

This turned around a little bit for the 8/8.1 and 10 mobile OS releases but not by much. A lot of stuff just wasn't possible on a Windows phone, even though the garden experience was exceptional.