How did Social Darwinism support Nazi ideology?

Darwinism, as you probably know, is the idea that creatures grow and adapt to all the stresses of life and our wolrd and in doing so, allow future generations to flourish.

Survival of the fittest was not Darwin's quote, but rather Herbert Spencer's, who said that if things need to change to survive, than those creatures we see today must have been the ones who changed the best, or were the fittest to survive. He created social Darwinism, saying that governments should not restrict big businesses, because those businesses that are fit and ready to survive will, and those who aren't won't.

In America, we used that with our racial issues by saying that the race that is physically sstronger and ready to adapt to its environment (whities), will find success, and those who fail socially (darkies) must have been inferior. It justified putting down minorities.