Final answer:
Great Zimbabwe's kingdom grew wealthy by leveraging its strategic position to control and tax the trade between local goldfields and the distant markets of the Swahili city-states, connecting the Southern African interior to a wider trade network.
Step-by-step explanation:
The East African kingdom that grew rich by demanding a tribute on all goods traded in the region was Great Zimbabwe. Trade was the driving force behind Great Zimbabwe's wealth and power. Strategically located at the head of the Sabi River valley, the capital thrived off the commerce between the goldfields and Sofala, a prominent Swahili trade center. The wealth of Great Zimbabwe was significantly boosted by gold, which, along with other commodities such as ivory and copper, was traded for luxury goods like Chinese porcelain and Persian faience. The kingdom solidified its control over local and regional trade, connecting the southern African interior to the East African coast and beyond, into the network of international trade extending to Asia and Arabia.