Well, the Nazis were stupid and used hydrogen instead of helium. The Hindenburg, pride of Nazi Germany, was full of rich people when it blew up in New Jersey, so who really cares anyway?
It's also worth noting that it wasn't the hydrogen that caused the fire. The Hindenburg had an aluminium skin. It began having degradation issues, so they painted it. The paint was iron oxide based. Aluminium and iron oxide are the 2 main ingredients in thermite.
Analysis of the video shows that it was the skin burning off. It would have gone up almost as badly, even if filled with helium.
Well they weren’t totally stupid, they couldn’t get helium because the US restricted them from getting it as the largest supplier. The plan was originally to use helium, but they went with the second best option.