They seek global domination through the zombication of the young via the slow, but effective process of MMORPG sales. You can corrupt many young minds with 1, but you can corrupt hundreds of thousands of minds through thousands of MMORPG’s.

From a marketing/domination standpoint it makes perfect sense:
-Make online game that never ends and turns people into zombies
-Sell game for a wad of cash.
-Continue to charge a fee every month to all your zombie members (to help fund war efforts)
-When money stops coming in, make another game to not lose your zombies. In fact, probably best to just make the game in advance so that they can get sick of it and just start paying for your new game right away.

Sadly, even the crappy ones make $$$ because there is always somebody who wants to be the guy who has spent hundreds of hours mastering it, for geeky bragging rights.