How did social darwinism become a factor in the new imperialism?

Social Darwinism, Imperialism was the natural expansion and success of a well-evolved culture, and this expansion would help remove or improve underperforming lifestyles.

Social Darwinism

Only the best survive. The idea that humans, like animals and plants, compete in a struggle for existence in which natural selection results in "survival of the fittest."

Social Darwinism was used to justify imperialism, racism, and laissez-faire (i.e., conservative) social and economic policies.

d. dr. francis collins