https://en.wikipedia.org/wiki/Iron_metallurgy_in_Africa
https://en.wikipedia.org/wiki/Laterite
https://en.wikipedia.org/wiki/Bloomery
https://en.wikipedia.org/wiki/Iron_Age#Africa
-Notice the ore used is available in a lot of places. Approximately one third of the planet's soil sits on laterite. The closest areas that are relatively laterite-poor are in north-central and far south-western Africa, far north and far south of the area in question.
-Notice the iron reduction method does not require limestone, and does not require modern blast furnace temperatures.
-Notice the fuel is charcoal. Any place with plants or trees will work. (You won't see many smelters in the middle of the desert, that's for sure.)
-Notice before they were out competed by the vintage 20th century blast furnace tech, there were small cottage iron making industries all across the continent. edit -all across every inhabited continent actually, but we are talking about Africa here. The industrial revolution changed everything so rapidly the modern person has no clue what people could do for themselves before Sears and Walmart.
-Granted it appears a place in Eastern Africa called "Nubia" were exporting iron and iron products to their neighbors in this time frame, which may have suppressed industrial Iron-making in their neighbors.
-Granted bloomery processes are kind of time consuming so you couldn't scale up without a large number of smiths.
As an Engineer, I don't have a clue where you are coming up with this stuff. Africa may have mostly skipped the Bronze Age and moved straight into the Iron Age in the first millennium BCE, but that does not mean they are somehow magically incapable of making iron. This is not complex stuff for a Smith. The problem with turning out huge quantities of iron is more likely structural/economic, and very likely NOT basic access to the precursors.