If that is the case, why was every person onboard Helios 522 still alive when the aircraft hit the ground?
Absolutely correct, the altitude and temperature is what probably killed this passenger - I believe hypoxia just erodes any reaction from a person relatively quickly until you loose consciousness, it is believed the majority of all those on Helios 522 were still alive when the aircraft impacted the ground. The fact he didn't fall out when the gear deployed probably rules out him being crushed he must have secured himself in the bay somehow.