Answer:
The main reason for its collapse is the war as well as Qin Shi Huang's son death.
Step-by-step explanation:
There are various events which leads to the fall of Qin dynasty. After the death of first emperor Qin Shi Huang of the Qin dynasty, civil war broke out. During this civil war, drought and floods also destroy the economic conditions of the empire. Qin Shi Huang's son death collapse the Qin dynasty completely because there was no one from the Qin Shi Huang's family which take over the throne. When there was no one who ruled on the empire so Gaozu who was a general declaring himself Emperor of the new Han dynasty on 202 BC and it was the end of Qin dynasty.