The people most likely to grasp that wealth can be created are the ones who are good at making things, the craftsmen. Their hand-made objects become … - Paul Graham

The answer (or at least the proximate cause) may be that the Europeans rode on the crest of a powerful new idea: allowing those who made a lot of money to keep it.

Now we think of the middle class as people who are neither rich nor poor, but originally they were a distinct group. In a feudal society, there are just two classes: a warrior aristocracy, and the serfs who work their estates. The middle class were a new, third group who lived in towns and supported themselves by manufacturing and trade.

The other thing that's different about the real world [compared to high school] is that it's much larger. In a large enough pool, even the smallest minorities can achieve a critical mass if they clump together.