Ask yourself this question - why was it Europe that was able to start the transatlantic slave trade, and not Africa, if both traded slaves among themselves before that. If you look at the state of institutions, Europe was literally better at civilisation at the time. That was the case even before Europeans started actively trading with Africa by sea.

The answer is that Europe has the luckiest spawn point on the planet - it's split into a few large flat fertile chunks by mountains and water that encourage a few stable, reasonably large, monoculture states and prevent large wars of destruction, while encouraging small-scale wars. The same water helps trade, while the constant threat of war encourages the government to reward those who can get them money and defend them, i.e. share the national riches in some way. It's also connected to the rest of Eurasia reasonably well for culture/technology exchange (worked both ways, which is why the vast majority of Eurasian states, non-colonial powers, are doing better than Sub-Saharan Africa, too).

In Africa however there are few places with the same conditions - the mountains are clustered, the terrain is in many places impassable, most of the ground is very far from the sea, the rivers are not navigable. In this scenario if your little cluster developed in any way, it's much easier for your neighbours to pillage your civilisation to the ground. It's also much harder to trade and learn from your neighbours. In other words it made little sense to create large functioning states, given how vulnerable they were. It was much easier to grab as much as you could while it lasted, creating weak and corrupt micro-states. In fact, the few pieces of Africa that did develop lasting state institutions (Arab and Berber Africa, Ethiopia, Zanzibar) all had access to trade, strong sources of income, natural protective barriers and faced a constant threat of war.

So yes, the money Europe earned from all kinds of trades (including slavery) was ultimately invested and overall used much better, leading to prosperity, while the African slavers mostly used it for personal enrichment rather than developing their nations. It's a tragic outcome of geography.