Same for steam engines: it turns out Watt spent most of his effort on getting components manufactured and having the associated manufacturing processes developed. The basic idea of the steam engine had been around for a long time prior. You can ask the same question of Romans and electricity. They had all the necessary tech: glass for insulators, acid for batteries, metallurgy for wire etc.
Reminds me of John Salvatier's point about the "surprising level of detail" in reality, i.e. yes, the idea that "steam can drive a wheel" is simple enough, but you have to get a lot of small details right that don't make it into textbooks like reliable manufacturing tolerances.
I'm regularly imagining what I would actually be able to accomplish if I went back in time 200-2000 years. Details are always the problem. It reminds you how little you know, but also helps you to form a background interest in engineering, metallurgy, geology, chemistry, etc.
You have to make the machine to make the machine that allows you to make your final product.
You would still have the advantage of being able to beeline past technological dead ends, but you still have to build up the industrial base. Even then you run into problems with chemicals simply not being available on an industrial scale because previously there was no need for them. The world is a massively complex interconnected system.
Related quote from the computer game Alpha Centauri:
"Technological advance is an inherently iterative process. One does not simply take sand from the beach and produce a [computer chip]. We use crude tools to fashion better tools, and then our better tools to fashion more precise tools, and so on. Each minor refinement is a step in the process, and all of the steps must be taken."
The people who authored quotes for Alpha Centauri deserve some sort of award. It's probably the most quoted game I've seen, and those quotes are all pretty insightful.
About how one development leads to the next and so on. And how a break in the chain (eg. New York blackout of 1977) could lead to the entire collapse. The underlying topic is still, or even more, relevant with today's technological dependance.
