By increasing productivity through industrialization and technology advancements, and by doing those things before the rest of the world. (and by having economic systems that accomplished this faster/more effectively than others, possibly also as the result of plagues that decimated the population a few times)
You seem to be ignoring the human labor part that happened around then and the backbreaking work that they did. Robots didn't get it done nor did the 40 hour work week.
yes, but if you think your great-great grandparents had it easy, well you should ask around and read books written around that time. I think you forget the standards for everyone was just plain misery not long ago.
I have actually read a bit about how one of my great-great grandfathers lived, and it didn't seem he was miserable and could arguably be said to be better off.
More to the point though, the question was how the West got rich. I was talking about the last ~1000 years, maybe a little less, of history in the western world and how their development led in part to the differences in development today. What that has to do with how many ancestors 100 years ago were miserable or not doesn't really connect.
Taking on that subject though, I have this idea that people regardless of situations are on a grand scheme equally miserable. Whether living in a cave 20,000 years ago or a New York penthouse, if you had a way to quantify misery I doubt you would be able to find a significant discrepancy. (corollary: much of the depression and other mental illnesses experienced today are a result of the drastically different environment and set of hardships experienced compared to the ones we evolved in)
The West was still pretty poor even 200 years ago. Going back 1000 years ago makes no difference. Economic development and the fact that almost everyone benefited from it in the West is very, very recent History.
The reduction in population of some of those epidemics made fairly large improvements in the survivors' lives and can be seen as the stimulus in a lot of the progression of Europe.
Progress that led to wealth in the west wan't just the industrial revolution(s), it started long before and was the effect of several technological and social developments.
In case nobody gets the joke: the economic system was the plague.