Since he was completely outnumbered and outpowered, there was nothing that the king of the Poppin Kingdom could do except surrender.
There was a part of him that wanted to see if he could fight with the knight order, but he knew that this was risky.
Surrendering gave him a better chance of survival.
Surrendering gave him more options.
So it was better to surrender.
One had to admit that even if the king of the Poppin Kingdom was a terrible tyrant, he was still someone capable enough to sit on the throne as a tyrant without being deposed that easily.
If it wasn't for the fact that someone much more powerful interfered this time, the king of the Poppin Kingdom never would have been taken off his throne like this.
It was only because of the interference of the Kite Kingdom that this even happened.