Dust on the Throne: The Search for Buddhism in Modern India (2023) by Douglas Ober, unfortunately, did not begin with an analysis of why Buddhism failed to thrive in India, the land that gave the world Buddhism.
Received wisdom is that Buddhism disappeared from India, the land of its birth, between the 13th and 14th centuries.
Ober, instead, chose to argue that there was actually a revival of Buddhism in 19th- and 20th-century India.
I am not sure if his thesis is sustainable, as most Buddhists in India are actually Dalits (the politically correct term for untouchables).
In the 1961 census, there were 3.2 million Buddhists in India. (P 323).
It was the great Indian leader, Ambedkar, who led the Dalits to convert to Buddhism. He saw Buddhism as the only option for a just and egalitarian Indian society. (P 187).
He converted in 1956. By 1961, nearly 3 million of his followers had declared themselves Buddhists.