Who could have settle dit? Egyptians... Numidians... maybe (hellenist) greeks... maybe carthaginians, if we becoem adventerous... Arabs... Portuguese... Dutch... English - well they did, to an extent. Okay, I must agree. That does seem odd indeed.
I guess it is because Afrcia was largely ignroed anyways. seeminglky neither the arabs nor the portuguese had any ressources to go form teh coats into the hinterland, while sudan/numidia was a major block for all possible egyptien or hellenist attempts...