There is no way that it was a clueless smoker that ignited all of these fires. Given that you are in a lavatory, there is water available -- so it is very easy to fully extinguish a cigarette. Just snub it in some water in the basin. Fully out.
Maybe a clueless smoker could have started fire #1 by tossing a lit fag into the trash bin. But after that, the smoker would have made sure to fully extinguish the cigarette, so would not have started fires 2-4.