The part about Rayleigh and Crocus, especially now that you watched 1149, is to highlight that they knew about this info and their professions/livelihoods reflect that. Crocus, who you were a bit stumped on, made it so that he can live inside Laboon, a detail I forgot myself, so that he's able to survive just like Rayleigh given the rising tides.
The Wano part also reflects their knowledge of this coming prophecy as we learned on Zou that they created the poneglyphs/are heavily tied to the void century. They erected walls and built Wano very high up so that it would be safe. The same can be said for Zou (all safe way up on a giant elephant) and of course the celestials are in the safest point in the world, at the top of the red line thousands of meters in the sky.