He made sure to drag the bound-up snake demon king through the portal too. After all, this demon king of wrath has become part of his loot. He doesn't want to lose any of his loot. That's what made them fight in the first place. It will be ironic if he forgets the demon king of wrath.
The entire divine plane began to collapse immediately after he left the plane with the Authority of the Celestial Supreme. The divine plane has lost its anchor so it has lost its purpose.
The only option that the divine plane has is the tree father in the mortal realm. Now the tree father has become the only god in the entire plane. It has to rely on the tree father for its continued existence.