Aryan invasion theory cannot help for conversion. In fact, aryans once liked this theory because they could equate them with aryans. In fact, hitler call germans, aryans. So called Tamil books were written only after 100BC or so. By the time aryans entered Tamil Nadu, copied relgious texts, remade them as if they are their own. We could get reference to aryan invasion if the texts written before the sea engulfed the 'kumari kandam'. But you could see the word 'aryan' in Tamil texts. Wars with aryans also mentioned there.
