Why is islam predominate in northern africa today?

Islam entered the African continent from North African countries such as Morocco and Egypt, and was one of the first regions to be conquered by the early Arab-Islamic expansion (7th and 8th centuries). From the tenth to the sixteenth centuries, Muslim merchants contributed to the emergence of important kingdoms in West Africa, which flourished thanks to the caravan trade that crossed the Sahara into contact with the steppes and savannas of West Sudan and central Africa.

b europeans take corn to africa. corn becomes an important crop there.