Unless you are an American with Greek roots, you probably didn’t notice that voters in Greece elected what is called a “far-left populist party.” The voters favored a government for the average citizen, not the bankers. They saw the past government as too interested in cutting as much government spending as possible in order to pay debts, no matter the harm to average citizens.
This kind of policy is called “austerity” and was demanded by the European Union for loaning the Greek government money to keep it going. It was hoped that austerity would promote economic growth by cutting spending. As it turned out, massive unemployment from the job cuts offset any growth.
Past Greek governments borrowed more than they should. Also, of course, creditors lent more than they should. Corruption leading to massive avoidance of taxes by the wealthy contributed as well. Those are legitimate targets for fixing.
But citizens in a democracy will take only so much unemployment and austerity, especially if they perceive that the wealthy are not paying their fair share. They will then search for relief at the voting polls. As the Greeks did.