A bit unfair criticism to what was a logical idea:
air traffic would increase over the decades, thus to decrease congestion at airports make a larger plane;
a larger plane is also in theory more efficient due to economies of scale: fewer crew per passenger, less wind resistance per passenger, lower airport landing charges per passsenger ;
true more airports might be built but there are always going to be main hubs such as London, Paris, Dubai, Singapore, L.A., New York, Mumbai, Beijing, etc, which are the initial and final destinations for many passengers.

I think the two causes of failure were the advent of more fuel-efficient motors, and the less than efficient management of a European Union company which apparently for political reasons, is obliged to spread assembly production over France, Germany and Spain.