In the end, Tuo Bihan hid his suspicions and didn't press. That little lass had the Celestial Eyes of Spiritual Divinity and had clearly bought half the sect somehow. Even under their watchful eyes, he still left without anyone noticing. Even Qi Lang had admitted that he was under orders to not report Wei Wuyin's arrival by Wei Wuyin.
It was quite stupefyingly impressive how embedded Wei Wuyin was in the sect in just four years. While his status of Heavenly King was bestowed to him, he truly gripped immense power and influence in the sect in such a short period of time.
If Tuo Bihan knew that even the Grand Imperial Sages had been corrupted, who knew whether he would laugh or cry to an early grave.