As others have said, they had Maemo/Meego. As the owner of a N900 myself, it was really good, but they decided not to bet on it for some inexplicable reason.
I think the reason was a lack of thriving app ecosystem. Microsoft seemed like a much better bet in that regard, they just messed it up in incredible ways.
I am sure the reason came from Microsoft. They have mastered outplacement as an offensive weapon.