The communist party participated in the Greek government after Greece was liberated. The reason they quit? They disagreed with the disarmament of their military wing.

Another thing that deserves mention is that the civil war actually started years before the Nazis left. The communists had been attacking not only the Nazis, but also right-wing resistance groups (EDES, PAO, EKKA)! The Brits actually brokered a ceasefire in early 1944, which the communists broke 2 months later by murdering resistance leader Psarros (https://en.wikipedia.org/wiki/Dimitrios_Psarros).

There is no assuming involved; they didn't simply "want" a violent take over, they actually tried to do it and lost.