The questions about the early route of the aircraft after loss of contact are relevant because this information would prove the aircraft was under control. The MH370 autopilot is not going to give multiple heading changes on its own.
If the aircraft was under control, high jacking and mass murder is the only answer, whether by a pilot or some other party.
the autopilot can't follow a flight plan? The autopilot could fly a route from the FMC (e.g. to approach or hold entry WP to Banda Aceh alternate airport) and after reaching the last programmed waypoint would maintain the last heading until pilot intervention… or fuel starvation.
(disclaimer: speculation)