I don't blame Tsipiras alone, clearly his predecessors hold much of the blame too - they were a basket case before he was elected. However they thought they could just impose their will on everyone else because they wanted it, failing to understand that they were the supplicants. As another saying goes: beggars can't be choosers. Greece needs a bailout far more than the creditors need to bailout Greece. When you go bankrupt and the bank comes to an agreement with you and says they're willing to let you continue living in your home so long as you don't retire in your fifties then you don't spit in their face.
I don't know who said this quote first, but it sums the situation up perfectly:
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