Diplomatic Civs often grant you extra happiness. And what do you do with that extra happiness? There are only so many celebrations you can get, so the best sink for it is going over your settlement limit. The warmongering aspect of Diplomatic should not be underestimated.Yeah, I guess my point generally is that I don't really understand the model for Chola. You get bonuses for trade, but they are rather weak compared to their naval abilities. One of their unique buildings helps you build naval units, which further encourages you to Command and Conquer. If I could recategorize them, I would label them Militaristic/Economic. This feels more honest to me than Economic/Diplomatic, which to me, implies a more peaceful approach.
I'll repeat, though, that the Economic/Resource Legacy path in Exploration is far too entirely dependent on map generation for any success. You either find 0 resources available without major effort (war or settling Far Away with devious routes for the Treasure Fleets) or too few Resources reachable in time to complete the path (and no way at all to speed up the fleets in map speed or generation time) or you find just enough resources at your doorstep and complete the entire path before the Age is 2/3 over.
Much of the map-dependency goes away, though, if you embrace your inner conquistador and be ready to take those resources by force. You often do not even have to do protracted battles against big cities, there usually will be lightly defended towns with plenty of resources.
I think the economic legacy in Exploration is not intended to be entirely peaceful. The distant lands are not supposed to be free real estate.
... Or that might be just me trying to justify my warmongering