This already happened a few years ago, people voted for Tsipras. The fact that populism has swept over the (so-called) western world in recent years shows this is not just a Greek issue, the rise of populism is a reaction to the marginalization and effective dismantlement of the middle class by the global market and its elites. Obama pointed that out quite clearly in a recent rather insightful, if not slightly hypocritical, speech in Athens. As long as this doesn't change, soon the whole developed world will start electing politicians that will make them Great again.