My guess is they are not flying over the Sinai for illogical reasons, the seats just can't be sold, and they have to show due diligence on being "careful".

No matter the final determination of the cause, this is going to tank tourism even further and hurt Sisi. Cairo bookings are already in the crapper and the bombing of the Mexican convoy in the desert was bad but somewhat manageable through PR spin.

The Egyptians, Airbus, Russians, and EU onlookers are all going to press for a conclusive determination of the cause and a very public release of the results.

If it turns out an engine took a dump or the airframe split, Sisi will demand that the word gets out in order to deflect any concerns of insurgent action in his country. He'll play the Russians to ensure they release those details if that's how it shakes out. Russia can point a finger at Airbus and blame the OEM.

If it turns out to be terrorism, Airbus will be all over that to prove its aircraft was airworthy.

The Russian government has little to lose, no matter how this plays out, so it's pretty even odds that the cause will be released, if it can be conclusively determined.