Hydrogen fuel cell cars are a boondoggle, the efficiency of generating electricity, using it to crack water into H and O, liquefying the hydrogen and distributing it makes it so, not to mention building the fueling infrastructure that currently doesn't exist.
Yes an electric charging infrastructure also needs building but the backbone of a national grid already exists it just needs a charger plugging into it which is far easier than adding high pressure / low temperature hydrogen storage, etc to petrol stations.
As for 'green' energy, it's cheaper and more efficient to 'clean up' a single point of generation - the power station than millions of smaller generation points - cars.
As for why they are subsidised and have lower tax? That's capitalism, money is a big evolutionary driving force now thanks to our choice of society, people won;t do what's good for them on their own, they'll do what's cheap for them and works hence the ev breaks.