Why did the inhabitants of Northern China equally allow themselves to be conquered by the Khitan in the X century

Why did the inhabitants of Northern China equally allow themselves to be conquered by the Khitan in the X century, the Jurchen in the XII, the Mongols in the XIII, and the Manchus in the XVII century? Why did they prefer to have barbarian overlords over Southern Song rulers?

The peoples of Northern and Southern China, even in the Han era, differed no less than the inhabitants of the Western and Eastern Roman empires. The split of China into the North and the South is similar to the split of the Mediterranean into the West and the East – into “Franks” and “Romans”. Therefore, the Chinese northerners resisted the southerners as stubbornly as the Byzantines resisted the Catholic knights.