You are just assuming some kind of malicious filtering happening purportedly in interviews and the like. A perfectly plausible and likely the only explanation i

You are just assuming some kind of malicious filtering happening purportedly in interviews and the like. A perfectly plausible and likely the only explanation is that historically, yes the caste system led to the lower castes being denied economic opportunities that translates to them being less likely to have the resources to attain higher education abroad. The above explanation does not require the mental gymnastics of some sort of coordinated effort by upper caste interviewers to filter out lower caste people.