Jet fuel is flammable too - the public weren’t used to disasters of that nature occurring, and manned flight was still relatively new - most airship accidents of the era are attributable to pilot error.
The fact that helium is a byproduct of natural gas extraction is beside the point. Heavier than air flight is an environmentally horrendous way of getting about, and if you can stop expending so much energy just to stay up, then you can achieve a lower carbon footprint even using conventional fuel.
The Hindenburg was designed to use helium, incidentally, but the US wouldn’t sell it to them because of Nazi-related embargoes or something.
