Get a load of this:

The problem here is that the West African nations are literally the descendants of slave traders. How many people there trace their family wealth to selling slaves? The business district in Lagos, Nigeria, the Tinubu square is named after a slave trader. This is what it says on Wikipedia:

Following British victory in the Reduction of Lagos, the British removed Oba Kosoko from his throne and replaced him with Akitoye, who was backed by Tinubu. The British had Akitoye sign the 1852 Treaty Between Great Britain and Lagos, which required Lagosians to abolish the Atlantic slave trade. However, Tinubu covertly persisted in operating the slave trade with Brazilian and European merchants, in violation of the treaty, and Akitoye willingly overlooked this.^[6] British consul Benjamin Campbelldenounced Tinubu’s economic hegemony over Lagos and her secret slave-trading, and she came into conflict with the British and rival Lagos merchants.^[5]

Hence, the British colonialists were instrumental in bringing an end to the slave trade in the area. Matter of fact, the European countries throughout the eighteenth and nineteenth century were undoing a system of dependencies that existed for millennia ever since the first complex societies and bronze making appeared. Abolishing slavery in the colonies or the US south was part of the same process.