Popular conversion is possible- though probably not among the merchants. It'd follow the same course it did in Kerala where the Catholic converts were of the lowest castes.Conversion to Christianity would be against their interests and they'd know it. The only time Christianity in India didn't follow this pattern was with the Syrian Orthodox and they adopted Christianity almost two thousand years ago, when Hinduism was a lot more flexible before it had developed survival measures to cope with the monotheistic religions.
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What excactly do you mean by survival measure?