The Underworld has its own plans, and the Demon Clan has its own ideas.
God of Desire's understanding of the struggle for destiny far exceeded that of Si Ren, and it was even possible that he had already begun laying out his strategies hundreds of years ago.
Logically speaking, with God of Desire having prepared for so long, he should have had ample contingency plans in place for any and all emergencies, allowing him to crush humanity with overwhelming force the moment the war began.
Chapter 1283