A big part of why they went with Microsoft was that the Android market is already saturated, as opposed to the WP market, where they have a chance to catch an ecosystem in its infancy and become the dominant player in that ecosystem.
Also, they're selling Fire tablets at below cost. That'd be horrifying for Nokia's finances. Not to mention that Kindle Fire's sales crashed hard after the initial holiday rush.
http://www.readwriteweb.com/mobile/2012/05/amazons-kindle-fi...
Meanwhile, LG, Sony, Acer, etc. etc. are in losses with Android and HTC is barely ekeing out a small profit. That demonstrates, how smart Nokia was not to just into this pool
Asymco has good data on who is making profits in the industry: http://www.asymco.com/2012/05/03/the-phone-market-in-2012-a-...
This.