Comment by etiennebausson

This reasoning would lead to such absurd results in real life, and I am thankful no courts of any country or jurisdiction follow this logic.

For those reading: this is the difference between proximate cause and actual cause. Yes it's true that but for the fire being started in the first place, the fire would not have rekindled. But once professional firefighters arrive to put out the fire, it's not foreseeable by a normal person that the fire could be rekindled, so that person wouldn't be liable. The harm is too remote. The firefighters may even be grossly negligent because they are professionals, intervened, and the fire rekindled. A person negligently failing to fully extinguish their own fire would lead to liability, though.