I don't think the above commenter wrote that all of precolonial Africa had a single culture, only that precolonial cultures evidently did not have cultures with long standing businesses - at least as we understand businesses them today.
Often with extreme prejudice, such as when the British destroyed and burned Benin City to the ground, destroyed large parts of its walls, which were once a single fortification threading through the city measuring four times the length of the Great Wall of China, looted it's art, which then for a long time was "explained away" because the bronze sculptures were a lot more advanced than Europeans liked to think Africans were capable of, ignoring the descriptions of Benin City from those who'd been there.
The result was that for a long time the idea of what pre-colonial Africa was like was based on ignoring the things the colonial powers had stolen (the Benin Bronzes were sometimes assumed to have been brought by Portuguese traders, for example; a more comfortable idea than Africans making bronze statues), and looking at the aftermath of colonial destruction as evidence of lack of large structures and cities.
yeah, it is their own fault, lmao.