The reason why Feng Du chose this opportunity to bury the heavens and refine all living beings was because he had calculated that the Martial Dao Prime Body would be held back by the Great Emperor of the Heavenly Court and would not be free.
However, he underestimated the determination of the Martial Dao Prime Body!
He had not expected that even faced with the choice of fighting one against two and going against the Heavenly Court and Netherworld, the Martial Dao Prime Body would still want to stop him!
Feng Du did not understand Desolate Martial's Dao.
Desolate Martial established his Dao and imparted martial arts to all living beings.
The original intention of the Martial Dao was for all living beings in the world to cultivate and become immortals.
The Great Dao was long and the path ahead was uncertain. The further Desolate Martial walked, the more he would never forget the original intention of the Martial Dao!