I have dealt with four vehicle fires over the years and one was a faulty fuel pump putting too much gas into the carb and the other three were electrical shorts. I have always carried around a fire extinguisher and basic wrenches and tools and with the electrical shorts disconecting the battery terminal was all it took to save the day.
With motorhomes there are both the engine problems and internal appliances that could cause a fire. Odds of it happening are extremely rare and would bet that most RV related deaths are the result of a traffic accident.