If only their country wouldn't be so eager to enter in selfdestructive accords with its suzerain, right now half of cars on entire planet could be produced in Japan. Or maybe half of Japan would be bombed to rubble because that's how this surerain is when someone weaker don't obey.
I don't think that foreign power told them to focus on Hydrogen. Japan is still searching for an economic wunderwaffe. Like in the 90s when they tried to leapfrog the west on software by focusing their entire computer industry on Prolog.
I mean it's all related in the end. If Japan bet wrong with hydrogen, then the obvious fix would be to partner up with Chinese companies like CATL for batteries.