2016 Kerala post-election CSDS survey. BJP is really NDA. The Ezhavas vote for NDA most likely is due to Ezhavas based BDJS running as an ally of BJP
Given what I know about Kerala's racial/religious/caste demographics and political status quo, it makes sense that the BJP would be stronger among upper-caste Hindus and younger voters, who I imagine would be more receptive to Hindu identity politics and populist (Indian) nationalism respectively. Kerala and Tamil Nadu seem to have very strong regional parties/coalitions, which partly explains why Kerala is so left-wing relative to other states.