Andraz:
You dont appreciate just how vicious storms can get in southern africa.
On the same day they had hailstones bigger than cricket balls in Joburg, think what those could do to an engine. Pure speculation at this stage of course but these storms have a well deserved reputation, historically several aircraft have been literally torn apart in them. A double flameout is not beyond the realms of possibility and would be consistent with the apparant low energy of the crash.