Part of it is to do with emigration from India to the US (where money talks) during the communist Cold War era when there was discrimination against upper caste

Part of it is to do with emigration from India to the US (where money talks) during the communist Cold War era when there was discrimination against upper castes in India (and note that an upper caste person may not have much money). In the UK and other English speaking countries, immigration was varied and across a much longer time period with predominantly middle class and skilled people.