Actually there were cities/large towns in parts of Africa below the Sahara that had cities of 50,000 and more before the European slavers and colonialists came in. Actually, some rulers in those cities captured Africans in the bush to sell to the European and Arab slavers.
Yup. The old capital of Benin was huge, and as was the casse in cities throughout Africa and in the muzzie world, the slave trade was just another business. Enslaving members of other tribes would not typically go unanswered, and that city in particular turned into a ghost town in less than 100 years after the discovery of America.