As Star Lord Yisuan said, the challenge issued to Emperor Tianyang by Fire Virtue Star Lord was permitted by him; otherwise, with Fire Virtue Star Lord's temperament, he absolutely wouldn't make a move at this time.
It is well known that the Great River Country Lord has ruled over this ancient country for thousands of years, and is definitely a mastermind in his own right. He knows when to act according to circumstances; otherwise, when Pei Xuanjing took action and annihilated the strong ones from their faction in the Great Ming World, the other side's reaction wouldn't have been seeking peace. Instead, it would have led to an everlasting feud, and the two sides would have become enemies.
Pei Xuanjing needed him to make a move and confront the Great Ancient Emperor and Ancient Emperor Saint Lord of this realm to verify certain things.