I recall reading that when EPO tried to go back to the Karaiskakis, Olympiakos told them no and I was under the impression that was due to their on going feud with EPO.
I think EPO's original intention was to move the team to Crete but the stadium there needed work and wasn't done in time (and I guess they're not even trying to get it done now) so they've ended up back at OAKA.