Comment by maxbond
Hydrogen is not picky about fuel air mixture; it will explode at any concentration between 4% and 74% (in air). I rewatched the footage and it sure looks like an explosion to me.
https://www.youtube.com/watch?v=OetzoO3Csj4
The thermite paint hypothesis is interesting but a bunch of hydrogen airships exploded. The Hindenburg was partly made from metal recovered from the R101. The R101 exploded on her maiden voyage.
At 24 seconds in, that looks indeed fast. But still not what one would expect of "Knallgas" going boom.