I don't think it's hard. As a kid, I didn't know about floating point but derived it on my own. It seemed logical to just add another number that represented where the binary point was. I'm sure Babagge would have got there if his iteration time wasn't so slow. He really should have made a small general purpose computer as simple as possible just to experiment with.
Babbage's work pre-dated mass production. Today, production people look at something like that, and ask "how many different parts"? Because banging out a lot of the same part has been a routine job for the last century. Babbage was too early for that. Parts required much hand work and craftsmanship. Metal part manufacturing did not scale yet. It was possible to build Babbage's parts using clockmaking techniques, but it would have required a lot of clockmakers.
Ely Terry had a mass production clock business in the US by 1804, but the gears were wooden. Apprentices made rough clock wheels, and better workers finished them more precisely with hand tools. Precision stamping was still in the future, awaiting the widespread ability of steel in the 1880s.
The Ingersoll dollar watch (1896), "The Watch that made the Dollar Famous", was probably the first high-volume mass produced product with part complexity and precision comparable to what Babbage needed. A few years later, the Computing-Tabulating-Recording company, the predecessor of IBM, was manufacturing the first commercial electromechanical computing devices in quantity. After that, there was steady progress.
Those were the days when New England was to the world what Guangdong is now.
