Don't know that there was enough public support for grexit last year. There was for less austerity. But for leaving the euro? Syriza promised to stay in the euro and reduce austerity and was voted into office. When they were pressured to impose austerity measures and the new elections were called syriza won again. Greeks could have voted for parties that would leave the euro then. But didn't.
None of the mainstream parties were in favor of the Grexit (perhaps with the exception of the ultra-left KKE and the ultra-right Golden Dawn). The Popular Unity party failed to cross the threshold. Syriza was rather interested in getting more favorable terms from the Eurozone, and they used the threat of Grexit quite effectively.
