It's a cheap game affordable by people of multiple class.
The game only has 1 key concept, being building. It's sandbox nature after that allows for people who enjoy different things to all enjoy the same game.
It is a game sold online and thus available to most nations around the world for purchase.
The game also has online functions which attract players and keep people of diverse backgrounds in contact.
The online forum is easy to use, available to everyone and mostly anonymous, which attracts people of different backgrounds and enables them to act how they choose with relative freedom.
It's not surprising its relatively diverse.