My guess would be that a lot of non-Indians at these companies are rejected on the basis of "vibes"; which is slightly different from racism as I explain below, although it probably ends up having the same net effect as overt racism.

As an Indian, I've observed that collectivism and subservience towards authority figures are taught as virtues; this obviously makes it quite easy for employers to extract unreasonable demands such as long working hours, transgressions of ethical limits, things that are "bad", but that generates benefits for the employer.

On the other hand, European and American societies generally focus on individualism and autonomy, which obviously causes a conflict when an Indian hiring manager sees anything other than complete deference to them as a threat, and proceeds to reject such candidates.