There are any number of rational reasons why Nokia would want to release their own Android device. You'll probably find them on the Web in any number of blogs so I won't rehash them now.
However, that boat has sailed as far as I'm concerned and Nokia is all about Windows Phone especially now that Microsoft has bought the handset business from Nokia. So, why Android now?
Again, many reasons why but that was in the past. The Lumia line is all about Windows Phone. Why would Microsoft get in on Android? "If you can't beat them, join them" thinking?
Nah. Nokia's Android is a forked version. Without Google apps and services. It'll be stacked with Microsoft's own apps and cloud offerings.
With its own flavor of Android, Microsoft has the ability to take ownership of Google's mobile crown jewel and used it for its own benefit while hoping to put a hurt on Google in any number of ways.
One, Microsoft would be forking Android further. It's not necessarily a bad thing for the platform but it could be bad from a monetization standpoint for Google. Should Microsoft gain a sizable share of the Android market, those mobile warriors would be using Microsoft's apps and services - allowing Microsoft to monetize those users instead of Google. And all those user information that Microsoft collects from its own Android users? Yup, Google will get none of that.
Furthermore, it could potentially drive some users towards Windows Phone, some but not a lot.
It's actually a very clever plan and will really cost Microsoft nothing. Look at how Amazon is doing with Kindle. Albeit no one knows how well Amazon is doing all but by some accounts, it has a nice chunk of the Android tablet market.
And to make matters worse for Google and Android device makers using its Android, Microsoft could release Office just for its own Android devices - maybe tablets as well.
Microsoft and Nokia's Android play can be summed up in one word: sabotage. Only time will tell how it works out. Will it drive Android users towards Windows Phone because of the similar UI on the Nokia Android device to the Windows version or will Microsoft successfully drive a big wedge in the Android platform and grab control from Google.
Of course, all of this could be nothing at all as well. All of this could have just been a ploy by Microsoft to extort more money, eventually a takeover, and once Microsoft is done digesting the handset division from the Finnish company, it'll put an end to this Android experiment.
However, I hope that isn't the case. We always like more players in the mobile market. That means more competition.