Setting the fire like that was reckless. I wonder if he could claim temporary insanity due to the medical state he was in. Heat injuries can have a mental impact.
"Setting fires was illegal regardless of the circumstances"
I'm not sure this is the whole picute. Isn't there a legal concept that you can break the law to prevent a further harm? Like speeding on the way to the hospital. I'm betting if he set a distress fire in the fire ring, they wouldn't be after him. So that might be misleading.
Anyways, my biggest takeaway is that you can make a mistake and be completely fucked for the rest of your life. It's safer, legally, to just stay inside and not participate in anything due to legal risks. As perverse as it sounds, it almost seems the hiker would have been better off dying and let his estate sue everybody. At least it seems the legal system prefers it that way.