Two obvious points: one, hydrogen-powered cars (where the H2 is obtained by standard hydrolysis) have been around in Europe since the 1970s. The problem has always been the energy required to create H2 is greater than the energy subsequently released in the engine of the car, plus the pressurized tank to contain liquid H2 is really, really heavy. No one wants a fireball of burning H2 in an auto accident — remember the Hindenberg? Two, the notion of any kind of “ether” was disproved by the Michelson-Morley experiment (which is ironic as they were actually trying to prove its existence) and by all other interferometer experiments since then.
So you don’t have to believe in conspiracy theories or magic woo-woo; it’s enough to know a little bit about the real world. The problems with H2 have always been creation, distribution, and storage. That’s why Europe never got behind large-scale usage. The costs were simply prohibitive — as Arnold discovered when he had his dream of a hydrogen powered California not so long ago. There’s no conspiracy; just basic economics. But that’s less sexy and scary and thrilling, so the conspiracy theorists will continue to believe as they always do because they have a psychological need to do so.