The accidental death hypothesis is the most straightforward in its logic, if not in its specifics.

A person who enters a cave system for any purpose faces real risks — disorientation, injury, equipment failure, exhaustion.

In a cave this deep, at this altitude, an injury that impaired mobility would rapidly become life-threatening.

A person who fell and broke a leg in the deep section of Hourglass Cave, more than a thousand feet from the entrance with no one knowing where they were, would have little chance of rescue and would face death from exposure and dehydration within days.

A person who became separated from their light source in the dark zone of the cave would have no ability to find the way out.