We regularly fly in airplanes full of fuel, and if they catch fire in flight the odds of any survivors is extremely poor.
Hot air balloons, with no hydrogen, catch fire now and then and everyone dies.
Planes have big engines and can generate a great deal of lift. That means their fuel can be housed inside safe tanks of metal.
An airship needs to have thin lining around its lifting gas in order to fly. One can make the argument that recent progress in materials engineering makes it possible to have material that is thin but strong -- and I know next to nothing about the state of materials engineering -- but that does not change the fact that for the past few decades, a hydrogen airship would have introduced a great deal of risk for no good reason.
I think the point is moot: at a typical speed where airline accidents happen, these metal tanks will be punctured and catch fire.
TWA800 likely exploded due to a short circuit that ignited fuel-air vapor inside the fuel tank.
Fuel burns. That's why so much effort is expended in airplanes to try and stop that from happening. The designers learn from experience.
A helium Zeppelin isn't safe from fire, either. Once the canvas catches fire, it's going down in flames. Frankly I doubt whether having hydrogen in it or not makes any real difference. I've seen the clips on the news where hot air balloons, with no hydrogen, catch fire and what happens (everybody dies).
There's no reason to believe that hydrogen Zeppelins could not go through a similar learning process as aircraft that would make them just as safe as airliners are today.
There's no reason this cannot apply to Zeppelins.
Their conclusion: combination of the doping (paint) and hydrogen.
The reasoning: the burn without hydrogen took twice as long, indicating that it wasn't solely the doping's "fault".