The Ancient Greek....true, there are not many facts, but there is plenty of circumstantial evidence.
1/ crew & passengers have all had their backgrounds checked, nothing suspicious found.
2/ there was a sudden event that disabled communication systems and possibly autopilot.
3/ one hour later satcom powers up.
4/ the aircraft continues to fuel exhaustion. When ever this happens it is usually due to decompression and crew incapacitation. Four past incidents I can think of. So,
5/ crew incapacitation.