It's hard to say the austerity measures are to blame for their economic downturn. The Greek economy has by some measures continued on the path started by the financial crisis and by some measures improved (bank capitalisation, budget surplus before debt payments). If they have a recession at the same time as austerity it's a bit of a stretch to say the cutbacks ruined the economy. I'd also say that Syriza is a pretty hard left wing party, of whose proposals I've seen little that doesn't amount to "borrow more and spend more". Their election rhetoric was "we shouldn't have to repay because that's insulting to us".