Hydrogen Fuel Cell is about 4x less efficient than BEV because you lose about half the initial energy making the hydrogen and half of that going back to electricity again. It's just very hard to come back from that if you have an alternative that uses the electricity directly.

They're still better than conventional ICE (as long as the hydrogen is made from renewable energy) but just on energy alone BEVs are about 88% efficient, FCEVs 22% and ICE 18% efficient.