Mostly kidding, but basically it's because they think that finally they'll have a boss who will kick their lazy coworkers into shape, or fire them. They'll be assholes to those OTHER people. The people who deserve it. Of course assholes are usually just assholes, and not necessarily competent or fair assholes. Odds are they're going to kick you too.
In politics it's clear who your lazy coworkers are, who those OTHERS are. It's blah people and other moochers. Promise to give them a good kick and you get 40% of the vote.
