As to why there aren’t many Buddhists in India, you have to realize that the nature of Buddhism, especially in its original form, made it quite vulnerable to political forces. The monks were concentrated in monastic communities that were dependent on support by the secular community and the indulgence of the secular authorities. They were forbidden by their vows to till the land, touch money, or own more than the bare necessities. They couldn’t take up arms in defense. They could only survive in a favorable political and social environment.
India went through many periods when the secular climate turned very much against the Buddhists, not least of which were the invasions of the White Huns and the Mongols. During those hard times, India was almost entirely emptied of Buddhists, who took refuge in the Himalayas and other neighboring areas that were more supportive. The current %0.8 actually represents a modern increase in the Buddhist population.
More to the point of the question, though, there is no Buddha who decides the fate of this one or that one. The entire import of the teaching of karma is that it is one’s own actions that condition how one experiences reality.