Its simple, most servers with high populations or that last a long time are usually run by hackers, they know how to hack, so they know how to protect their server from hackers too. So when a newer/better server pops up and starts taking players from another, the server owner of the "dying" server will go hack the newer/better server to try and get their players back instead of giving a s*** about why people were leaving in the first place. They are afraid of competition they can't beat, so they attack it in the most pathetic way possible, but this is not true of all server owners who are hackers, some actually like this game and are smart enough to use their competition to get ideas to make their own server better when people start getting bored and wanting to leave.