those little shits should be THANKFUL that it wasn't me doing it, cos that guy was retarded as shit fly licking shit.
if i wanted to set entire train full of ppl on fire, i'd use concealed bag of flammable liquid, probably not gasoline as it vaporizes too fast and might not ignite, then i'd have a tube going into my shoe and i'd have a hole at bottom of my shoe or side/back. then valve on top in my pocket. i turn the valve and flammable liquid starts slowly pouring out, without anyone even noticing. then i'd walk from one side of the train to other while liquid is pouring out.
when i lit it, then entire train would go up in flames within seconds! THAT is how you do it!

A more effective approach would have been to create a subtle self sustaining fire.
By drilling a small hole in the gasoline bottle and placing it under a seat, the fuel would slowly drain onto the floor without suspicion, people would think it's just a leak or wouldn't even notice it. near the bottle, place a makeshift incendiary device made of a cigarette, with 3 matchsticks carefully positioned in the middle of the cigarette taped around it, wrap the half of the cigarette with toilet paper starting from where the matchsticks were positioned, everything kept in place by a rubber band. as the cigarette burns down to the matchsticks, the friction would ignite them, which in turn would set the toilet paper aflame. the burning paper would then ignite the gasoline. this method ensures a delayed, low risk ignition without the need for a direct flame, simply drop the burning makeshift improvised incendiary device, near the gasoline bottle under the seat and immediately exit the train. the slow burn buys you time for a safe escape before it ignites next to the gasoline puddle, causing maximum damage significantly lowering the risk of collateral damage and getting caught.