State the reason why caste can not determine the election results in India

No party wins the votes of all the voters of a caste or community. When people say the caste is a 'vote bank' of one party, it usually, means that a large proportion of voters from that caste vote for that, party.

no Parliamentary Constituency in the country has a clear majority of one single caste. So, every candidate and party needs to win the confidence of more than one caste and community to win elections.