I was at that Hindenburg site, (well sort of), hard to find the airfield, a motel with a blimp on the sign let's you know you're near, but once you find the field and hangers, it's all behind a locked gate.
Recently a scientist found a piece of the cover fabric on the site and found that it was extremely flammable. His theory is that the Hindeburg was struck by lightning and ignited. That there was no sabotage or conspiracy. He also felt that the fire started on the Starboard side and went up over the top near the hydrogen vent and consumed the port side. That's why it appears to be the vent that's the source of the first flame, and takes into account the eyewitness reports from the side we don't see in the newsreels.
We'll never know.
