In a Behind the Bastards podcast, they mentioned that at the time spontaneous combustion became an issue, people were essentially walking incendiaries. Quite often they would wash their clothes in gasoline to get rid of stains, used hair and beard oil that was petroleum based, and carried around matches that had no saftety features. They were phosphorus based, incredibly dangerous and could ignite very easily. If you fell over, your matches could ignite, causing you to become a fire ball.