Zimbabwe had a huge kingdom going before colonization. They even had pyramids and walls n shit + they traded with civilisations around them like the Swahili big time. They were fine back. Colonization disrupted this. The Swazi have their nice little kingdom that is unique to them, even the South Africans don like or want to dick with them. They are/have being fine for like ever. Btw, this again goes back to geography and climate. SA has Mediterranean climate whilst Swaziland doesn't. Meaning, humans tend to have commonality will people we can chit chat withbabout the weather and consequently knowledge gets passed betwen us.
The Congo, dude do you even how big and rough the terrain is. Going back to geography. Rough terrain means people are locked in one region and only interact with immediate neighbors. It's like why the fuck would I want to fight the terrain, hippos n shit so I can chit chat with you about the weather? I am fine where I am. If you got some urgent shit you wanna talk to me about. Come see me, I am not coming to you. Consequently again, zero interaction means shit tgat i know or shit that you know does not get passed betwen us. It was just to much of a hassle. Besides if they were really stumped about shit... Necessity is the mother of all inventions ... They invented shit to deal with immediate problem.
Haiti... I am blaming Napoleon on this one and french colonial assimilation! Dude was to broke to give a shit about the colony. Colony was broke from the get go. The slaves took over but they were so assimilated to french culture that they became colonialist themselves. They were black but not "Africa" more like french akin to how black in New Orleans sometimes thought they were back in the day. This attitude is still prevalent to this day. My 2¢.
Mozambique... What a shit show. Portuguese basically carried everything that they could carry after they colonized them. Kitchen sink, trash cans, everything. Mozambique had to start all over. They got their shit together. Portugal was like ... Oh hell no! Came back with the Russians and fucked that country up again. Civil war, re-education camps etc and we it is what it is now.