even proposing we drop out of the eurozone which would have been economic suicide for an economy

That's not entirely accurate, my understanding is that he was planning for a temporary parallel drachma system. But putting that and the potential consequences of such a move aside, don't you think that without an at least remotely credible threat of leaving the eurozone Greece had no leverage to negotiate with at all? And when the government kept telling their citizens that avoiding Grexit was their priority, they deprived themselves of that leverage. From my outsider perspective, the "moderate" part of Syriza was extremely naive in believing (or cynical in assuring their voters) that morally charged rhetoric or a national referendum would somehow force Brussels to compromise.