People stay under the name Padawan when they do that because they don't want their name associated with their actions, they don't want to be bothered to be responsible for their actions, or they don't want the history associated with their name to follow them into the server. A lot of them wreak havoc because they're too bored to restrain themselves; they take every opportunity to kill because it feels good and helps ease the boredom. Others do it just because they enjoy winning or having power over someone else, even if it's just in a video game. Most of them are either too selfish to restrain themselves from easily satisfying their needs, or they don't think they're actually doing significant harm by ruining the experience for new players.
The reason it happens more on our server is because we have very few people banned. We usually don't ban for laming unless it's serious and we see it first hand. That being said, don't hesitate to private message an admin in-game when the laming is going on and you want it stopped. If there aren't admins on when you need them and the laming is very serious, let us know what happened on the forums. Screenshots and timestamps + time zones are helpful so that we can look things up in the server log, too.