Intelligence and bravery are considered heroic traits because a person with these characteristics wouldnt be afraid to deal with high pressure or dangerous situations. Think of firefighters charging into a burning building to save someones life, or soldiers in war using their intelligence to give themselves a strategic advantage over the enemy. Hopefully this helps a little bit.
It is unknown what caused the fire. Some say that some kids played with a match or that it was a cigarette that Johnny or Ponyboy didn't put out. Johnny and Ponyboy help to save some schoolchildren from the burning church. When they try to get out, a piece of timber falls on top of Johnny, breaking his back.
