> 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.