Why were the Swahili city states so wealthy and powerful?

The Swahili city-states were wealthy and powerful due to their strategic location along the Indian ocean trade routes, which allowed for lucrative trade in goods such as ivory, gold, and spices. They also profited from taxing passing trade ships and acting as intermediaries in the trade between the interior of Africa and the Middle East, India, and Southeast Asia. Additionally, their urban centers were organized and prosperous, with skilled craftsmen, bustling markets, and well-developed infrastructure.