How did Islam and the beliefs of indigenous societies fuse among African people?

Well the beginnings of the Islamic faith were in Mecca and Medina which are two cities in Saudi Arabia. Saudi Arabia is not far from many African countries who consider themselves part of the Middle East like Egypt, Libya, etc ... Also, at the time of Islam's growth, many people followed the faith and made it part of their lifestyle. It spread by word of mouth and through customs and traditions. Even at that time, the religion spread as far out as to Spain in the west. Local kings and leaders of nearby African countries welcomed the religion, further spreading it and it even became the subject of empires trying to take over empires.