Islam did not spread the same way throughout all of Africa. In North Africa, Islam spread by conquest. In West Africa and along the Indian Ocean, Islam spread by contact between Muslim merchants and local Non-Muslims.
Typically, Arab merchants spread goods from place to place. (That's what merchants do.) However, merchants also facilitate cultural diffusion which allows for religions to move between countries. It was through Arab merchants that Islam disseminated through West Africa, East Africa, and much of Indonesia.
ISIS
I've heard that merchants and business people's kind of habits, practices and moral values have caused them to turn into Islam. That's a good example however to refute the slander which claims that Islam had spread by sword.
muslim merchants travild sending religion with them
Merchants and teachers help spread Buddism.
Merchants and teachers help spread Buddism.
Muslim merchants set up trading posts throughout southeast Asia and taught Islam to people there.
Islam first spread along TRADE ROUTES since merchants could often bring the religion to places too far away to effectively conquer.
The main religion of the Swahili people is Islam. Islam spread to the Swahili coast through trade and interactions with Arab merchants, leading to the majority of Swahili people practicing the Islamic faith.
Trade routes across the Sahara desert allowed for the exchange of goods and ideas, facilitating the spread of Islam in Africa. Muslim merchants and scholars played a role in spreading the religion through their interactions with local communities and rulers, influencing them to convert to Islam.
Ben Brierley raped Allah :'D