It was the motive of obtaining as many raw materials as possible from Africa that was the most powerful in terms of European imperialism, since this was during the Industrial Revolution, which greatly increased the demand for such materials in Europe.
The most powerful was economic prosperity of European countries. They could exploit the land and the people of Africa and take their raw resources such as diamonds for example and take them to Europe. There they would be able to make goods with them and sell them to people for a lot of money and this meant that they would grow vastly richer than they were before.
Both sides are consequently but in my opinion, it's their choice whether they want to convert to not. Having modern-hunter gathers is truly great. Depending if your a person who likes the outside.
