The Demon Race thought it was idiotic for the Dragon Race to promote capable people from low-status backgrounds.
In fact, because the Dragon Race's bloodline was so dominant, they had never cared about bloodline issues.
A low-status background didn't mean someone was weak. The Dragon Race appointed people based on merit, so putting capable people in positions of power made perfect sense.
But the Demon Race used this to spread rumors about the Dragon Race, Xiamier, and the nobles of Zhu Xia.
They claimed they were incompetent and corrupt, and couldn't govern the world.
Then they launched an attack and rebelled.
At the same time, they allied with humanity. Some humans had been infiltrated at the time, but not all of them.
Humans found people with strong body odor disgusting, and the Demon Race smelled strongly.
Simply deceiving the Dragon Race was enough.
Saint George, the dragon-slaying hero, had set an ambush for the Dragon King. Though it failed, he became a symbol of resistance to the Dragon Race's rule.
He stirred up conflict between humans and the Dragon Race.
And conflict between true dragons and Dragonkin.
The Dragon Race's rule back then was basically hands-off. They would simply declare that a territory belonged to the true dragons, collect their treasures, then consider the matter settled.
The Dragon Race also demanded pure bloodlines, which was perfectly normal.
After that, the Demon Race began gradually conquering the forces that obeyed the Dragon Race.
The Dragon Race had no subordinate countries back then, but that didn't mean there weren't forces that willingly acted as their lackeys.
After all, the true dragons would come to collect protection money, then return to their caves and stay there.
If you had a problem and went to them for help, they usually wouldn't lift a finger.