Just my $.02
I don't think there is a significance about the lack of handover loss of communications.
That area has been known to have silent spots and sometimes you just have to fly until you hear Cairo and give them a call.
Maybe they didn't hear the Greeks, and had already changed to a Cairo frequency. I'm sure they knew what frequency they were going to be assigned.
I would go along with an earlier poster, that a device was installed at a location where security might not be as tough as CDG.
It could have been detonated by a timer (they really don't care when it blows), or by someone on board.
Look back at the crash out of Sharm El Sheikh.....many thought that was a trial run.