..."Why bother going to FL450 and then back to FL295 and making a lot of unexplained turns?"
If true, it could be a sign of a struggle in the cockpit. Because at the time, the airframe was too heavy to maintain FL450 and likely stalled, then dropped and was recovered at the lower altitude.
The experienced suicidal pilot/hijacker(s), behind locked armored door, after setting autopilot course to mid Indian ocean, could then have turned off the packs, (airframe pressurization) and leisurely asphyxiated along with the rest of the occupants during the 6 hours' phantom cruise. This gentle death would have spared them the adrenaline filled black-hole drama of violent impact on a moonless night after fuel exhaustion.
