No one questions that things have been going wrong in Greece for decades.
The problem is, completely regardless of whose fault it is, the conditions now imposed on Greece will strangulate Greek economy even further and thereby make the back payment of their debts even more improbable then it used to be. The Syriza idea of a haircut combined with other measures to leave room for the Greek economy to recuperate would, on the other hand, have increased the probability.
But that wouldn't have given the rich parts of Europe, most important Germany, the opportunity to plunder the remains of Greek property.
Which is, by the way, what renowned economists like Krugman and Stiglitz say, too.