Discontent also drives change of the status quo. Without discontent, those in power would be forever in power, discontent is a sign that government/society is failing the people. People in power do not become corrupt because they have power, they either were already corrupt, or become corrupt in the process of maintaining power. History has been replete with examples of tyrants, who ride in on a wave of public support, only to fall later due to the alienation of the public because of their paranoid policies to keep their hold on power. Thus a person who is corrupted by power isn't corrupted because he has some desire to "do more with their power", but rather they wish to maintain their current social status by any means necessary, which tends to lead to a discontented populous.