I agree we can't predict the future, so why hydrogen is the only synthetic fuel being discussed. There is a laundry list of contenders. Each with different properties, some exceeding hydrogen in terms of energy density, ease of storage, efficiency of production, and so on. Methanol, dimethyl ether, etc.

Manufacture of synthetic fuels pairs nicely with overproduction of cheap renewable energy sources, and some amount of it is necessary for a niche of applications that require energy density or other aspects of combustion.

So, exactly as you said, why should we pick winners wrt hydrogen vs any other synthetic fuel?