They're only simple because we take industrialization for granted.
Even if you got the idea for a safety bicycle earlier in history, things get a lot less simple when you have to make each chain link by hand.
(Speaking of, there's probably one or two rotational points in the chain, but maybe don't include all of them on your diagram.
)
Pre-industrialization the only one who could make a chain as fine, delicate, and strong as a bicycle chain would be a watch maker, or a locksmith, sometimes that's the same person.
And at the time they worked on what was considered the pinnacle of complex technology.
So I guess simplicity is relative.
Though... you could argue that the bicycle is a massive simplification of the horse.
A simplification that enabled the first true egalitarian mass mobilization of people.
Maybe I just negated my own point. Hard to tell because I kinda forgot what my point was.