Short answers, pulled from the story.
Buddhism declined gradually and ended around the 13th or 14th century. Records indicate that by the end of the twelfth century, Buddhism had further disappeared with destruction of monasteries and stupas.
Muslim conquests represented the first great iconoclastic invasion into the region from the 8th through 13th centuries. Turkic, Turkic-Mongolian, and Mongolian forces overtook northern Indian plains while rulers like Muhammad bin Bakhtiyar Khilji destroyed major centers such as Vikramashila around 1200.
Hindu sects like Vaishnavism and Shaivism grew increasingly popular during the Gupta Empire from the 4th to 6th century. Orthodox Brahmins gained power under Gahadavala and Sena dynasties and accepted Muslim rule in exchange for extirpation of Buddhism and repression of social sectors in revolt.
Major centers included Nalanda, Odantapuri, and Vikramashila which was destroyed by forces of Muhammad bin Bakhtiyar Khilji around 1200. Archaeologist Giovanni Verardi argues that monasteries from Sarnath to Vikramaśīla were not destroyed by Muslims but appropriated and transformed by Brahmans.
On the 14th of October 1956 in Nagpur he converted to Buddhism along with 365,000 followers. This event marked the beginning of mass-conversion ceremonies throughout India led by the Dalit Buddhist movement.