Nokia didn't have a choice to partner with anyone but Microsoft.
If they stayed with Symbian they were dead. MeeGo was dead before being born. Blackberry would have never partnered with them. Apple would have never partnered with them. This leaves Microsoft and Google.
If they choose Google they are now competing on the same platform against a much cheaper Korean and Chinese manufacturers and designers. I am sure they could have made a go of it, but the company would have shrunk and likely be in worse shape than they are now. Microsoft was desperate for a partner and champion, so it was a match made in heaven.
Now this doesn't say they won't die, but given where they were it was the best move to make.