Actually, Bai Zepei's plan wasn't to let Bai Ruozhu pretend to be the murderer; how could he bear to let his sister take such a risk?
Initially, he planned to pretend that he was framed and caught by the clan.
Judging from the perpetrator's method, the murderer needed someone with strong abilities, including the experts in Wei Hall. It's likely they want to strengthen themselves through these individuals, and Bai Zepei just happened to have recently passed the Enlightenment Tablet, revealing a glow of red tinged with purple. He has become a famous figure in the clan, which will inevitably attract the perpetrator's attention.
Besides, he personally has no martial arts or inner strength, which makes him an easier target.
