> The problem was that the engineering was a lot harder than he thought it was going to be
This is true of many (most?) innovations. E.g. the steam engine: people knew about steam power, and built primitive steam engines. Watt succeeded eventually in manufacturing one that had the right mix of reliability, power, cost, maintainability to be widely useful. E.g. the jet engine : Whittle conceived of turbine aircraft power during WW1, but didn't succeed in manufacturing a viable engine and putting it in a plane until the end of WW2.
A lot of similar things come into play if you ask questions like "Could the Romans have invented $X?"
Some cultural factors like slavery meant they were less interested in e.g. labor-saving inventions. And there probably were health and life sciences concepts you could introduce--but might have limited ability to prove. But, for the most part, there are technology trees that you can't really shortcut and, even with the right high-level knowledge, it's hard to accelerate things too mych.
This is true of many (most?) innovations. E.g. the steam engine: people knew about steam power, and built primitive steam engines. Watt succeeded eventually in manufacturing one that had the right mix of reliability, power, cost, maintainability to be widely useful. E.g. the jet engine : Whittle conceived of turbine aircraft power during WW1, but didn't succeed in manufacturing a viable engine and putting it in a plane until the end of WW2.