What if a counterfactual trend prevented any Middle-Eastern monotheists from forming a large-scale successful religion and Arab traders freely traded with the East African city-states without distinction; allowing fine Arabian horses and sailing vessels/methods to be adopted?
Could this lead to East African city-states sailing around the Cape and trading with the ironworking West Africans and developing into a civilization of coastal city-states with horse, iron, and later knowledge from the Library of Alexandria in the hands of the pagan Sultan of Egypt?
The Pagan Alliance (with Persia as the distant strongman) falters against crusaders until butterfly-enhanced mongol hordes devastate Europe.
Africa and Arabia remain a patchwork of Christian and Mongol dynasties assimilated into existing cultures, along with truly independent kingdoms, and have a Renaissance while similarly Hordified and far more decimated Europe stagnates.
Horde dynasties are scattered across the thrones from China to India to Persia to Arabia to Africa to Europe.
Europe staggers behind the African Renaissance and naval wars over the Atlantic Passage to the African colonies in North America lead to defeats which lead to a strange revolutionary movement (no need to reinvent radical republicanism after all) in Europe against the Horde-descended monarchs. A generation worth of on and off war is fought and the revolution suppressed, but the ideas have been spread. This encourages more cultural exchanges with Persia and India, long trading partners, and leads to naval confrontation with China over control of Indian harbors. This imperial phase is accompanied by a generation of reactionary moralists (reactionary to the excesses of the war period) in the most prominent African kingdom.
Does this sound interesting? coherent? plausible?