Why did our humanity built on top of old buildings flooded by earth and mud?

Mud flood is the general term used but I don’t care. It does not make any sense for our people in the 1800s to build on top of other buildings covered by layers of tons of mud and dirt and earth! And we don’t know what happened before? Why was so much earth on top of old buildings? Rain with earth, soil liquefaction or brought with machines? If you like my channel: ▸ Instagram: ▸ Patreon: (currently not posting new content) ▸ PayPal: ▸ Shop: ▸ Facebook: ▸Twitter: