I would imagine somebody has floated this idea before, but I wonder if the distraction of hydrogen rather than electric cars was a ploy by Japanese automakers to give them time to build up the cars / supply chain etc to switch to electric. Typically cars (at least in the US) take around 4-5 years of development to get to market, so rather than assuming the Japanese policy makers just made a dumb decision, it could be that they wanted to wait until domestic electric cars were widely available before pushing heavily on the transition.