Why exactly didn't Nokia pick Android again?

When Nokia was preparing to jump off its burning platform, it had the choice of two lifeboats: Android or Windows Phone. It picked Windows Phone, and I've never really understood why.

Some people say it's just because Microsoft bribed them with a few billion dollars. I'm not sure how plausible that is: I can't imagine Nokia would take some cash up front in exchange for settling for what it knew was a weaker platform. Over the long term that just doesn't make any sense.

The other explanation I've heard is that Android would somehow not allow Nokia to differentiate itself from the competition. This is patently ridiculous, since Android allows OEMs to differentiate themselves to a much larger degree than Windows Phone does. A Samsung and an HTC Android phone are much more differentiated from each other than a Samsung and an HTC Windows Phone: different skins, different screen resolutions, different processors, etc etc. The only way this makes sense is if Nokia simply assumed it would be the only manufacturer actually producing Windows Phones (not that unreasonable an assumption, as it turns out), and that the very fact of using Windows Phone would serve as a differentiator from rival OEMs all running Android.

Well, it's serving as a differentiator alright: just not a positive one. I think everyone understands at this point that the Lumias 800 and 900 are already differentiated by their hardware design to such an extent that they would have been pretty big hits if they were running Android instead of Windows Phone. Nokia could have charged to the front of the Android line on the strength of its flair for brilliant industrial design, but now they're stuck at the back, lashed to a platform that, if not on fire, is at the very least wobbly. Couldn't they have seen this coming?

Thoughts?