Hindu religions vary a bit becoz all if them have their different beliefs and so they go on those beliefs ! People of Hindu religion are found in India in a huge numbers, as India is a secular country that gives individuals a fundamental right " Right To Freedom Of Religion"
According to this people are free to make their own religion beliefs and follow them or follow any other religion. India allows its citizens to follow anything or beliefs of their wish so that's what is the resin why Hindu religion varies so much becoz people have made their own beliefs which has made the religion so different!