It's not that simple. Hong Xiuquan didn't possess some mass hypnosis device that broadcast hatred of the Qing to everyone in South China; there was already massive pent up resentment of the Qing, and their declining legitimacy in the face of humiliation at the hands of Western powers presented an opportunity for local elites to build up power centers around themselves. Once the war reaches Jiangnan, anti-Manchu nationalism is a much stronger pull for the Taiping than their weird religious stuff ever was, and resistance to the Manchu had a long history before Hong Xiuquan ever put brush to paper. I remember hearing one professor explain that the opening of new treaty ports gutted the porter trade, where young men would transport goods to the markets in Guangdong, and left many young men unemployed.