PASOK represented a certain patronage network. That network probably still survives even in latent form, and I don't think it can be taken over by SYRIZA, not that SYRIZA should necessarily want to inherit that kind of baggage. So it's quite possible that a new party will emerge from the core of that network.

Now, why SYRIZA cannot pick up the mantle of being the dominant center-left party, I don't know.

guaranteed to evoke a violent reaction from police is to challenge their right to "define the situation." --- David Graeber citing Marc Cooper