Maybe the learned a lesson from the Hindenburg.
Oh, the Germans knew that lesson well before the Hindenburg.
The lesson was that in the 1930s the United States had the only stockpile of Helium, and refused to sell it to the Germans because if Helium's strategic value, so Germany was forced to use Hydrogen for their Zeppelins.
Today Helium still has strategic value, but not for use in Zeppelins, for use as a supercooled liquid for making superconductors work. MRI machines use superconductors in their magnet coils, and require liquid Helium to function.