From what I recall I think Louis kept us from experiencing the worst of it, and that as Phoenix he did something to the land's aether or something that allowed the world to go back into an Astral state much faster? I'd have to double check that but going of memory that was the case.

If anything it just feels odd to me that Bahamut technically even counts as a calamity compared to the other ones. He did some damage but when we swing around in 2.0 things are mostly fine. Sure there's trouble with primals and beastmen but the cities are standing and managing to hold things together. Maybe it was hell in that 5 year timeskip? But ultimately Bahamut's calamity just doesn't feel like it should even count next to the others.