Accident or Conspiracy: Godhra

As shown in the movie the forensic report says petrol from inside the train is used to burn the coach. And the police says miscreants were using cloth pieces dipped in petrol and thrown on the train after breaking the window panes which caused the fire. Then why the lower side of the exterior of the coach was intact and did not catch the fire? The stone marks still visible on the color? Was not the petrol spilled on the exterior when thrown on the train? If so why it it did not catch the fire and instead only caught the fire from inside the coach? Then what about the inside petrol theory? Second contradictory fact! The guard says the coaches were heavily packed. There were about 200 people in the place of 72! He could not attend the ACP in the ill fated coach. Then how did the people with so big petrol cans entered the coach from the vestibule? Did not the passengers overpowered them? Barely there might be 4 to 5 persons might have entered that is also not possible due to the presence of so many passengers and they allowed them to enter inside and allowed them to burn them. And after igniting fire the culprits escaped unharmed from such a large mob.