Unless I'm missing something like a special event, it seems next to impossible to become Buddhist as Maurya normally. You start several percentage points below the amount of Buddhism required to convert, and the the territory in nearby places isn't enough to get you there. The only way it seems possible right now is if you release a bunch of Hindu territory right away to get to 20%. Considering it's a historical path for the Mauryas, as well as a achievement, meaning it's intended for it to be doable, there should be a more feasible way to do this, like through a mission tree or event.
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