What is the real reason why the White Snake was submerged by Jinshan?

Fahai detained Xu Xian and forced Bai Niangzi to flood Jinshan to kill people, so as to subdue the Second Demon. After all, Fahai was a snake catcher all his life and almost killed Xiaobai. After 700 years, Xiaobai hated stealing Fahai's elixir. Since then, the cause and effect of the three people have been thoroughly planted, so it is a cause and effect for Fahai to break up and surrender to Xiaobai in this life. ...