Tsipras was playing to lose: call a vote, and when it gets the expected "Yes" result step down and let someone else manage the continuing grinding austerity. But the Greeks voted "No", and now Tspiras is just standing there with his dick in his hand.
The problem is that Syriza has a democratic mandate to do the impossible: keep Greece on the Euro, but get relief from the troikia-imposed austerity. If Greece is really unwilling to leave the Euro, though, they have exactly zero negotiating leverage. If Germany has decided that it would rather see a Greek exit than debt relief, there isn't even that potential leverage. Staying in the Euro means unconditional surrender to the troika, and austerity forever.