Horrifying secret: Why was the Song Dynasty a notorious training ground for corrupt officials?

Besides Qin Hui, considered the "foremost treacherous minister in history," the Song dynasty also produced a series of officials with less than stellar reputations, such as Cai Jing, Tong Guan, and Gu Zidao. Because of the exceptionally large number of treacherous and sycophantic officials, whose actions harmed the country and its people so severely, the Song dynasty is also referred to by later generations as a "training ground for treacherous officials" in history.