Fang Rui understood Zhou Guangyi better than Zhou Guangyi did of him. After succeeding twice, Fang Rui doubted that his trick would work a third time. He had decided that he would face Zhou Guangyi in a direct confrontation to determine victory.
But did that mean that he would put his dirtiness aside? Of course not! In this situation, Fang Rui suddenly facing Zhou Guangyi righteously in a direct confrontation was a dirty move.