I have been saying this since the referendum was announced: Greece can either accept austerity and stay in the Euro, or reject it and get kicked out of it. There was never another third option to begin with.
Syriza's promise was dishonest as hell, since they insisted to their fellow citizens that they could get everything they wanted: Euro membership and no austerity. And Greeks actually believed it, which is the problematic part here. They either deluded theirselves or got lied to. In either case, these negotiations were handled disastrously, and the Euro referendum was dishonest as hell.
That being said, EU's have been handling this crysis horribly, managing to be far too meddling (imposing draconian conditions into Greece) and far too little meddling at the same time (not improving Greek governance nor dismantling its clientelar network), making for a truthly horrible paradox. It is creating an important problem in order to solve an urgent one, so to speak.
I strongly believe that at this point another properly made referendum ought to be made. Greeks should be able to choose whetever to stay inside the Euro with these austere conditions, or break appart from it, no fantasy "inside the euro with no austerity" option. And the EU should grow a pair of balls for once, and start to assume direct control of the anti-corruption and justice departments of its members, "national sovereignity" be damned, corrupt Southern Europe politicians spending money as they saw fit was what created this mess in the first place.