It wasn't obvious in 1780 if you could build a steam engine that would be reliable and small enough to move itself, for example. Or if you can produce enough st

It wasn't obvious in 1780 if you could build a steam engine that would be reliable and small enough to move itself, for example. Or if you can produce enough steel rails to build a real railway network. It took 50 years of progress to find out that steam-powered railway was indeed viable. (For a modern parallel - we haven't built a small, portable nuclear reactor ever. The closest you get are nuclear-powered submarines, but no nuclear trucks.)