There was nothing to market, the N900 is more of a devkit and not suited for the masses.
So it was lack of marketing and a complicated device.
But if it had the dumbed down UI - like that of the N9, then comes marketing.
Where to market ? I don't know, I'm no expert.
I'd say wherever an iphone can be found the N9 has a place. Just a guess. You must have marketing, people won't chase you to buy your stuff.