Isn't South Asia already Hindu/Buddhist majority area? Well, perhaps it is possible keep Malesia and Indonesia as Buddhist and make Bengal lesser Islaimc.
I'm far from well versed in SE asian history, but perhaps a less tolerant Hindu Majapahit empire could prevent too many people in the area from converting to islam? Not sure how that would affect their their relations with the muslim merchants that regularly traded in the archipelago.
Isn't South Asia already Hindu/Buddhist majority area? Well, perhaps it is possible keep Malesia and Indonesia as Buddhist and make Bengal lesser Islaimc.