What was the outcome when europe became aware of the wealth of african kingdoms?

Once Europe found out about the wealth of the African Kingdoms, they started to slowly close in on them. Initially they started taking steps toward greater trade. Than missionaries were set on ground. And after that, they waited for suitable moment to overtake these kingdoms. As there were some tensions between the African Kingdoms and the Europeans already, some incidents happened when the African attacked Europeans, so the Europeans used that as an excuse to attack and colonize them.

Considering the military superiority of the European colonial powers, the African Kingdoms did not really stood any chance against them, and they were colonized relatively easy. Once the Europeans managed to colonize these kingdoms, they started to exploit the natural resources. They managed to make a very big wealth out of the African natural resources, using the local population to work for them as very cheap labor force, while they were taking the wealth out to their mother nations.