How Did Trade Really Prosper?

Trade in Africa was one of the major factors that made cities in African very wealthy. But how did trade become so popular, and how did trade in some places thrive opposed to other places? Did trade ever die out in Africa? Where did trade really prosper? And most importantly, how did Islam in Africa spread so quickly?
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The expansion of trade in Africa started in Azania, the modern day Swahili coast. For over one thousand years merchants have been gathering in Azania to trade, these merchants came from places such as,kkldfkdfkk Persia, Europe, and even China. A Greek Navigator learned that winds of the Northwestern Indian