http://www.zdnet.com/article/apple-takes-89-percent-of-all-s...
Apple is, I think like 20% of the smartphone market worldwide? But about 90% of the profits. And Samsung has to make almost all of its profits at sale, with Google making all the ongoing profits from stuff like Maps and app stores; if Microsoft cut Nokia in on any of that money (Nokia shipped mapping and music apps for their Windows Phone, for example), it may have looked like a better deal than Android offers Samsung currently.
Compare the sale price of Motorola Mobility to Lenovo (after Google stripped it of its patent portfolio) to how much money Nokia's handset business sold to Microsoft for without patents attached. What Elop did with Nokia's phone business may have been the best case scenario for it.
The first Samsung Galaxy was shipped in 2009[0] -- over a year before Elop was made CEO of Nokia [1] and nearly two years before the "Windows Phone Strategy" was announced.
In 2011 -- years before any strategy shift to either Windows or Android would have been able to be implemented, Samsung was already shipping more smartphones than anyone else -- including Apple [2]. Nokia didn't ship their first Windows Phone device until November 2011.
It would have been a Blackberry Storm kind of stupid to try taking on Samsung with Android as the platform. There's no compelling reason to pick Nokia over Samsung when the target market is just looking for value. At least with Windows Phone, there was some differentiation they could hope to appeal to consumers with.
[0] https://en.wikipedia.org/wiki/Samsung_Galaxy
[1] https://en.wikipedia.org/wiki/Stephen_Elop
[2] https://gigaom.com/2012/02/07/npd-apple-sold-most-smartphone...
Nokia hardware & Android software could have been a pretty killer combo, and a sufficient differentiator to get some extra profit margin; plus Nokia was (is) very experienced in producing at huge volume.
Unsurprisingly, the rump of Nokia that was not merged into Microsoft is now climbing on the Android bandwagon in a big way... but unfortunately everybody else now has a 10-year headstart.