Answer:
The depth of the answer truly depends on what class you're taking. But European nations colonized Africa mainly due to the rich natural resources they could use to profit from such as rubber and diamonds.
Explanation:
But, there were also other factors such as the concept of "Social Darwinism" which basically means that the stronger nations will progress and the weaker nations would be destroyed. So this meant that the European nations believed that they were strong and that they needed to progress by exploiting the "weaker" nations. Also, another concept was "The White Man's Burden" which was the idea that Africans or essentially any person of color was uncivilized and needed help. So the European nations sometimes used that as an excuse and basically acted as though it was the duty of the white people to civilize or "guide" the people of color.