Reaching right into the endgame, Sri Lanka may have been one of the less active civs but they knew a thing or two about survival. I don’t know whether it was strategic cunning or just knowing how to not piss people off (although taking land from the dying Mughals certainly helped), but even after Australian conquests in their homeland they just kept living on. Most civs would have lost an outpost in the Middle East pretty quickly, but Sri Lanka stayed on the peninsula like a chocolate stain on a white dress.
Boring perhaps, but they played well. As well as could have been expected of them.