what replaced it?
India is around 80% Hindu and 14% Muslim. Every other religion is quite small in numbers. (I think Buddhists are less than 1%.)
I’m not a fan of Nikki Haley, but she’s an American, born in South Carolina. Her immigrant parents were Sikhs (adherents of one of the minor religions in India). She says she converted to Christianity (her husband is a Methodist).
The Muslim invasions wiped it out.
Resurgent Hinduism & Sikhism replaced it. Happened roughly the 12th century.