> I didn’t know this but apparently when the British arrived, India was the wealthiest nation in the world by a hige margin

Note that this depends on what you mean by "wealthiest". India was wealthy the same way China and the USA are wealthy today, but not wealthy in the sense that Switzerland is a country of rich people.

Before the Industrial revolution, virtually almost all of the population (across the world) would have been peasants living in pretty primitive conditions, be it in Qing China or in Habsburg Spain. Urban populations were only a tenth of the population at best, and the wealthy merchants within them would of course be an even smaller minority.