The division of British India was. But the Republic of India, which is the entity under discussion, is a secular state.
British India was also a possession of the British crown, but the Republic of India is not. So stop confusing between the two.
Republic of in India is successor of Britsh India. Migration of people from both sides continued well after formation of republic of india on the basis of religion. Act of enemy properties and many other laws were passed in the Republic of India. So we can not wash our hands off when it comes to protection of Hindus.