The downfall of Mohenjo-Daro was caused by various reasons such as trade. Early theories were that the Harappans were wiped out by an invasion of the Indo-Aryans. The Harappans had flourishing internal and long-distance trade networks, this is why scientist has a theory that a decline in trade with Mesopotamia specifically trade in the lapis lazuli was an important factor in the downfall. Several layers of silt do show that the Harappans faced heavy floods and climate change specifically a decrease in rainfall. Scientist had a lot of reasonable theories for the downfall of Mohenjo-Daro. The most reasonable theory is the major climate change in a decrease in rainfall and weather because back then weather was unpredictable. Just as there were layers of silt proving that the Harappans had multiple floods. This is one of the reasons Mohenjo-Daro downfall. Trade was also involved in the downfall. The lapis lazuli was a very big factor in the downfall. As the Harappans expanded their trade to farther out places their city started to descend.