Theories: - Their engineers didn't think batteries were practical back in 1992 (reasonable). But by the early 2000s, batteries started to prove themselves, and fuel cells continued to struggle. But now those engineers from 1992 are in charge, and refuse to admit they've spent their career traveling a dead-end road. - They have some deep insight into other uses (trains, forklifts, jet-skis?) and need to build out the tech, and cars are their home. Germany is similarly stubborn about hydrogen trains too.

My money is on face. Toyota has spent too much money, and can't change until some senior people retire.