Why is Ralph so upset the boys let the fire go out?

The fire is the boys' only hope of rescue from the island. When the boys go hunting and instead of minding the fire as Ralph instructed them to do, a ship passes by the island. Had the fire been lit, the people on the ship may have seen the signal and rescued the boys. This is why Ralph is angry; the other boys' disobediance ruined his chance of escaping the island.