Which factor contributed to the decline of the han empire

By the 180s the Han court had grown weak, with debauched or disinterested emperors who lived only for amusement. Court eunuchs vied for power with the scholar-officials and army generals, at times even leading to massacres within the palace. In 189 CE, the warlord Dong Zhuo went as far to assassinate the 13-year-old Emperor Shao, putting Shao's younger brother on the throne instead.

But economically, the Han government had trouble collecting enough tax revenue to fund the court and to support the armies that defended China from external threats. I am not sure I this helps but, I hope it does.