1. The more massive you are the more inertia you can absorb but doffy went flying so couldn't have had absolutely absorbed the blowWhat if DD body absorb the attack.So impact on building was not enough.Also this building is stronger then building on fishman island
2 it wasn't a building it was a shipbthat was the size of an island and it was ae to remain intact for 900 years at the bottom of the sea under the pressure of the ocean. Its definitely more sturdy.