Stephen Elop explains how the Android-powered Nokia X fits into Microsoft's ecosystem

The basic idea behind the switch to Android is fairly simple (and one we put forth before), though it has never been outright admitted by Nokia - the Asha platform is too limited to be competitive in emerging markets. Windows Phone is okay, but until 8.1 is released, the platform doesn't offer dual-SIM support which tends to be a necessary feature in emerging markets. So, Nokia is using the X lineup as a "feeder system" into the higher-end Windows Phone devices. With that in mind, the Nokia X lineup has a UI that has obviously been inspired by Windows Phone, and integrates Microsoft services like OneDrive, Outlook, and Skype. 

Interestingly, Elop also somewhat admitted why Nokia didn't go with Android sooner in a chat with Re/code. While Elop didn't exactly take on the question directly, he implied that even if Nokia had gone with Android sooner, there would have been a fair chance that its devices would get lost in the shuffle, saying, "You see many other Android vendors who are in a very tough spot now building very credible if not great products but just unable to break through because of how that ecosystem has evolved." He went on to imply that only Samsung has been successful with Android, so the idea of Nokia going with Android would mean success is one that doesn't have a strong foundation. 

source: Re/code