1. Islam was founded in Saudi Arabia which is the center of the middle east. West Africa is near Saudi Arabia. Which made spreading the religion easier in terms of distance.
2. Islam says all humans are equal regardless of skin color. This made Black Africans more welcomed and respected when converting.
3. Africans kings ruled over non-Muslim people respectful, however, when Islam forbids something, the African Kings rules that over everyone. Such as killing or consuming alcohol. African Kings allowed celebrations and place of worships for non-Muslims.
Answer: Islam first came to West Africa as a slow and peaceful process, spread by Muslim traders and scholars. The early journeys across the Sahara were done in stages. Goods passed through chains of Muslim traders, purchased, finally, by local non-Muslims at the southern most end of the route.