I believe China took great pains under the Communists to move Han Chinese into Manchuria and other outlying areas, so that they wouldn't pose a breakaway nationalist threat to China.
The Manchurians were such a small group compared to the Chinese that it's surprising that they were able to conquer the country and hold onto it for centuries.
Good times, including ruthless conquest, often leads to a series of generations who see the opportunity for more leisure and take it. Now if you'll excuse me, I'm going to make sure my bottled water is cold for hydration after my massage.