The idea is create a heterogeneous society so the ruling elites can divide and conquer to remain in power. How many black people voted for Obomber twice even though he did absolutely nothing for them? Divide and conquer works. The Russian tsars did it. The Habsburgs did it. The communists did it. Our ruling class does it.
Genocidal murder is one of those things that cause people to live in disbelief. They just can’t believe it is happening until it’s over.