The Dark One connected Masteria and Earth in order to use the players as willing souls to train up the countless bodies that he would create to be the player avatars.
That much he understood, of course.
However, even if he had the power to entirely shut down their operation on Earth, which he didn't, it would make no sense to do so.
This army of avatars trained by the players was not the key point that made the Dark One win.
The Dark One won because he was the strongest being alive.
The Ancient Heroes were gone, and the ones that returned were too weak to face him. The other gods had been systematically eliminated. The Empress, the strongest woman alive, could not stand against him.
The natural course of events was for the Dark One to awaken and destroy the world. This natural course was sure to occur once more if he did not drastically change events, and the only way for him to do so would involve using the power of the playerbase.
