Why were ghana mali and songhai wealthy and prosperous empires

The Ghana, Mali and Songhai empires were mainly influential due to their share in trade in the region.

Explanation:

At the time, Northern Africa had access to one of the most desired trade routes in the world, but the two most important things traded were salt and gold. Gold was rare and difficult to find anywhere else, so traders from other countries would pay high prices for it. The empires mentioned above, charged taxes on merchants so for every transaction they got, they recieved a tax, and in this way, regulated trade and gained a lot of money which allowed them to flourish.