I think the reason was a lack of thriving app ecosystem. Microsoft seemed like a much better bet in that regard, they just messed it up in incredible ways.
I mean MS paid a stupid amount of money for Nokia too, i think that was they mayor influence. MS bought a platform to run Windows on for $10 billion if i remember correctly?
Microsoft was a horrible bet in that regard. Maemo was a natural development platform for many products (just straight out of my head: Mozilla, VMware and Rovio have all chosen it organically), to the point where there was plenty of notable stuff that was first developed on Nokia N900 and ported to Android/iOS afterwards, but only officially released for iOS and Android because Maemo was already abandoned as a consumer platform. Windows Phone had no such gravitational pull at all and its lack of software eventually became an internet meme.