Q. How exactly did Ash make all that money?
A. Ash made the first part of his fortune—a few thousand pounds—in India. He built the rest of his empire once he got back with that seed money.
The only thing I say in the book itself is that he traded rubies. I always imagined that Ash built his empire by learning to speak the local languages and getting a reputation for trading fairly… Which I very quickly figured out was my attempt to sanitize the getting of his wealth as much as I could. How fairly can you trade with people when your fellow countrymen are forcibly occupying their territory? Doesn’t matter how nice you are about it. It’s still money made on someone else’s spilled blood.
There are very few ways to make money in the nineteenth century that aren’t plain horrible in some fashion. Anyone who made money in international dealings was exploiting imperial positions and/or the slave trade. (Even if they didn’t traffic in slaves personally, trading indigo, sugar, rum, cotton…anything created by slave labor, really, would be problematic.)
Making money against the backdrop of the British Empire—however you sanitize it—almost certainly involved some degree of highly problematic behavior.
So the answer to the question is that Ash made money the way many of his countrymen did. He was nice about it, and never personally killed anyone, but he doesn’t deserve cookies for that.