Luca Fiore of Oasis magazine wrote an article on the Christians in Kerala titled, The Amazing Secrets of Kerala. I will briefly summarize this article presented by the eloquent Sandro Magister of Chiesa.
Legend has it that Saint Thomas the Apostle arrived and preached in Mylapore, India, not far from Madras, where he suffered martyrdom and where his tomb is kept today. Prior to his martyrdom Saint Thomas arrived in Kerala at about A.D. 52. The Christians in south west India called Thomas Christians due to the missionary efforts of Saint Thomas.
The Christians in Kerala are of the Syro-Malabar Rite within Catholicism and they constitute up to 20% of the population, where in the rest of India Christians are just a bit over 2%. Kerala is a pluralistic society where the majority of residents are Hindu, Muslims make up 25%, and Christians 20%. All the faiths live in peaceful harmony which is unlike some parts of India.
The state of Kerala is somewhat of an anomaly in India. With relative peace among the different faiths, Kerala also has the highest literacy rates in the country, over 90% compared to roughly 65% to the rest of India. Another exception is that Kerala is also the only government with Marxists in control. This coming from a state where the majority of the schools, from elementary to university levels, are predominantly Christian.
Conversions are not common, but when they occur, there is normally no violent reaction whether they convert to Christianity from Hinduism or Islam, though Pentecostals are the most militant and cause the most disturbance among the residents of all faiths. There are many reasons for conversion to Christianity, some convert because of the communal aspects of worship which is lacking in some Hindu strains. Other convert due to the love the converts witness that is carried out among Christians. But there is no definitive evidence of the major reasons behind conversions.