Growing an economy takes power, especially electricity. One major piece of infrastructure missing in most Sub-Saharan countries is a ubiquitous electric grid.
Only South Africa, Ghana, Kenya, and Gabon have 85% or better access to electricity, and while I don’t know first hand what the electric grid is like in all four of those countries I do know that while the Kenyan electric grid is widespread, in rural areas it is more common for there to be no power flowing on that grid than power. Thus the above map doesn’t tell the whole story.
Nor does the map tell anything the story of how these countries managed to pay for their electric grids, small or large. Electricity is not expensive per kilowatt hour, but building out an electric grid is a multi-billion dollar cost. I found the above map in the video below, which explains how Ghana build the world’s largest man-made lake to provide their electricity, why, and touches on how they paid for that infrastructure.