It was very important for Syriza to be seen as absolutely against Grexit.

The idea has to be established in the public minds that, when it happens, the govt did everything it could do. The general sense that I got from Greek voters (who formerly supported ND or PASOK or were now in To Potami's camp) was that they believed Varoufakis and Tsipras wanted out of the euro.

These sensibilities have to be managed. They don't change instantly.

Not to mention the fact that Greeks for the first time saw their politicians as fighting for them, which actually does address the gov'ts popularity.