Economies of scale, old sport. Remember when the Tesla model S was the only viable battery car on the market? It cost a heck of a lot more than $60k...... now they've reduced the price for the model 3, but it's also a lesser car. However, it has forced other car makers to start to produce equivalents....
The hydrogen fuel cell gives all the advantages of the battery electric drivechain - but without the need for a hugely expensive battery and without having its range compromised by hours of charging. I have no doubt that hydrogen fuel cells will be the powertrain of the future and the current battery-powered cars will be replaced longer term.
However, it means investment - and the current drive towards the Tesla view is focusing attention on the wrong area, IMHO. Why have trucks and buses with ranges compromised by needing to be charged for hours, when you can have a liquid fuel and "unlimited" range....... why replace millions of gas boilers with heat pumps when you can use the existing network to provide a clean alternative to natural gas? Why look for inefficient ways to store "green" energy, when it could be used to crack water and produce hydrogen.... a natural fuel store.