I think you're misunderstanding the pre-industrial-revolution world's attitude to trade secrets. "Learning a process inside and out, and reproducing it elsewhere" was not allowed, at least for high-value processes.

An example from within Europe: http://www.muranoglass.com/en/news-en/ten-facts-you-did-not-...

And I also suspect you're not understanding the relative value of those processes (glass, tea, porcelain, etc) to the economy of those areas vs the current relative value of the "product of thousands of engineers".