I agree with the general reaction among India's political scientists and the rest of the world that Narendra Modi's overwhelming victory in Gujarat -- five years after his government stood by and in some cases actively participated in a massacre of over 1000 Muslims -- is disturbing. But the BJP is likely to continue having success so long as it is perceived as the pragmatic party: the one that reduces crime (the regular sort, not the mini-genocide type) and bureaucracy. Modi has the reputation of being uncorrupted because after a lifetime in politics, he is not wealthy. He does not believe in the rule of law as it is conceived by elites, i.e. that everyone must have a fair trial. He advocates a more brutal form, in which those who are believed to have broken the law will be punished, even if requires a police shootout that takes out their wives as well.
The only reason that the Congress Party leads the national government's coalition is that the BJP overstepped its program of economic liberalization. Instead of just improving infrastructure and making it easier to run a business, they began to destroy tenements without offering the residents another place to live. It was this attitude of apparent malice toward the poor, coupled with the resentment among non-Hindus that an overtly Hindu supremacist party incurs, that led to the BJP's downfall nationally.
Within Gujarat, however, Modi's genuine success in improving business conditions overrode concerns about his being a rightwing nutjob. This is the problem of Indian politics: the choice seems to be between the Congress Party's economic stultification and the BJP's religious bigotry. (Because of the difficulty of finding a "fundamental" in Hinduism, a religion with almost as many major texts as gods, this bigotry sometimes takes weird turns that look like the sort of thing one would see in Saudi Arabia, such as police beating couples found cuddling in public and militants rioting against Valentine's Day as a wicked Western intrusion.) I don't think that Gujaratis who voted for Modi must all be Hindu supremacists as well; it's just that the benefits to them of having a well-paying private sector job outweigh the costs to their non-Hindu neighbors.