What was the sole purpose of British colonial rule in India?

India had an independent economy before the advent of Britishers. They came to India for the purpose of trade but eventually converted trade into exploitation. They exploited Indian resources for their own benefit. Britishers used Indian resources as raw materials for their own rapidly expanding industrial base. For example: Britishers forced Indian farmers to produce only Indigo in their farms so that they can export it to Europe at lower prices in order to meet the growing demand.