Why not to use portable heater while driving

My propane heater has a tip over switch! But, I don't have a motor home and can not see why I would need to run a propane heater while driving, nor would I. Then the article says something about he lost control, ran off the road in high winds, and could not stop because of water on the sides of the road??? I guess I don't get that part but, it sounds like this guy didn't know what the heck he was doing.