Why is World of Warcraft more popular than Lord of the Rings or DnD Online? I've never played but it looks expensive. What are they doing right? How do they get people to lay down the cash?
They made a more polished clone of Everquest using the setting from most popular RTS franchise in existence just as Everquest population was starting to crash and that RTS was peaking. It's not a particularly replicable formula.
Also it's starting to crash.