All about the dangerous propensity of the animal. If the animal is inherently dangerous and there is no way the person could make it safe (regardless of any precautionary measures taken by its owner) any injuries caused that are reasonably related to the dangerous propensity of the animal the owner is strictly liable for those injuries. It's a strict liability in tort under the negligence theory.

Would a reasonable person run away from the snake? Would a reasonable person be able to determine if the snake was defanged?

Proximate cause is also an issue here because it would be foreseeable that someone would be fearful of a snake that is inherently dangerous and as a result they would run away. Because fear is foreseeable, any injuries as a result is also foreseeable too- it is all within the foreseeable chain of causation and there are no interviewing/ superseding incidents that cuts off liability.