Railroads are unironically the solution, which is why the west built them all over their African empires, and left them behind when they left. Given the knowledge of this technology and its capabilities, and knowing that its a technology that actually plays to African strengths, they knew exactly what to do. Rail requires uninhabited land, which Africa has plenty of, can be laid simply with vast hand labor as the US did in its past, which Africa has plenty of, and only required importation of locomotives, which Africa could both afford to import, and very likely could guilt a fair amount of free units out as aid - God knows the western builders would love a new continent scale contract paid for by the Western governments.
So with all the cards stacked in their favor, Africans did what they did best. They ripped up signaling for scrap, stole equipment, rail and maintenance funds for their own personal benefit, and let the system degrade to the point that there's thousands of kilometers of unusable rail with billions of dollars in repairs required. They scammed themselves out of their great industrial era inheritance, and have nothing to show for it.