PASOK had something like 60% in the three prefectures of Crete in 2009 it is now winning, and it has dropped to something like a third of its vote now. The prefecture of Rodopi in Thrace was won by PASOK because there was a strong muslim minority candidate (50% in the prefecture). Syriza won neighboring Xanthi for the same reason...

The "center" that Syriza won is Athens, the Athens Basin area, and the exurbs and industrial towns (not to mention slums) surrounding Athens (heavy industry also is concentrated in the other two pink prefecture in the center, Boetia and the island of Evia). This is a big deal. It won across the board in Athens in all parts of town and the conglomeration except the richest. The little dot it won in Northern Greece is the Thessaloniki Metropolitan area. Between Athens and Thessaloniki, that's over half the population of Greece. It also won in the area in the Northern Peloponnese (Akhaia) where the third largest city in Greece is situated (Patras) and which is a deindustrialized city, in depression well before the current crisis. So Syriza won in the three largest cities in Greece.

KKE won in Samos- basically it won ~50% in the neighboring island of Ikaria, a Very Red island, populated by mostly crazy people (crazy in a nice way), which totalled something like >70% for the hard and harder left. That was enough to win the single seat.

Contrast and compare with 2009

The road of excess leads to the palace of wisdom - William Blake