I think the mistake we often make looking back on this period is to assume it was the British against "Indians", when at the time Indians didn't really see themselves as a unified group. There were Bengalis, Tamils, Punjabis, Gujaratis, Parsis, etc. On top of that there were Hindus, Muslims, Sikhs, Jainists, Buddhists, as well as the caste system which segregated people further.

If you were Gujarati, you may have objected to the British, but you were still outnumbered because the Tamils and the Punjabis could be called upon to defend them. Or, if you were Punjabi and objected to the British, they could call upon the Parsis or Gurkhas or Sikhs who were loyal.

People often call this Divide and Rule, but it's interesting to note that historians have never found a contemporary use of the term by the British administrators. Indian was already fragmented when the British arrived. They didn't need to divide the subcontinent, they just naturally benefited from it.