What were the reasons for decline of the Qin dynasty?

Answer 1

With the construction of the Great Wall and the fortifying of their army, they needed to have high taxes to raise money, many didn't like this especially the peasants. Also many thought the emperor, Qin ShiHaungdi was too harsh and he had no trouble killing those who stepped out of line the slightest. Between the taxes and the treatment, the many (mostly peasants) rebelled and the Qin began to decline

Answer 2

Three assassination attempts were made on Qin Shihuang's life, leading him to become paranoid and obsessed with immortality. He died in 210 BC, while on a trip to the far eastern reaches of his empire in an attempt to procure an elixir of immortality from Daoist magicians, who claimed the elixir was stuck on an island guarded by a sea monster. The chief eunuch, Zhao Gao, and the Prime Minister , Li Shi, hid the news of his death upon their return until they were able to alter his will to place on the throne the dead emperor's most pliable son, Huhai, who took the name of Qin Er Shi. They believed that they would be able to manipulate him to their own ends, and thus effectively control the empire. Qin Er Shi was, indeed, inept and pliable. He executed many ministers and imperial princes, continued massive building projects, enlarged the army, increased taxes, and arrested messengers who brought him bad news. As a result, men from all over China revolted, attacking officials, raising armies, and declaring themselves kings of seized territories.

Alex G.