Basic fact: for thousands of years, the big problem was making (or growing, catching, or mining) enough stuff. In the 20th century, that problem started to be solved. By the second half of the 20th century, the leading industrial nations had it solved. Then Asia caught up - Japan, Taiwan, S. Korea, and finally China. China was the big one, being a huge country. Suddenly there was overcapacity in almost everything.
Now, as I write occasionally, it just doesn't take that many people to make all the stuff. It's now possible to have a successful economy with a huge non-productive underclass. Economics and politics haven't caught up with this yet.