The error that, is was brutal Islam that force Mandingos to abandon their traditional animism is false. The kings of Manden as early as Sunjatta were Muslim back in the 12 to 13 century. The Kaabu Mandingos later contaminated their beliefs to the point that, the later generation adopted the prevalent local animism.
Below is the short history of Mansa Musa:http://www.newworldencyclopedia.org/entry/Mali_Empire
Musa I (Mansa Musa)
Sankore Mosque in Timbuktu, built of mud by traditional construction methods.
The first ruler from the Laye lineage was Kankan Musa, also known as Kango Musa. After an entire year without word from Abubakari II, he was crowned Mansa Musa. Mansa Musa was one of the first truly devout Muslims to lead the Mali Empire. He attempted to make Islam the faith of the nobility, but kept to the imperial tradition of not forcing it on the populace. He also made Id celebrations at the end of Ramadan a national ceremony. He could read and write Arabic and took an interest in the scholarly city of Timbuktu, which he peaceably annexed in 1324. Via one of the royal ladies of his court, Musa transformed Sankore from an informal madrasah into an Islamic university.
This established close links with other great centers of Islamic learning, with whom it exchanged teachers and students. The academy did not only teach Islamic Studies but also science. Ibn Battuta (1304 to 1368) visited Timbuktu (1352–1353) and praised its scholarship. In 1324, a Mandinka general known as Sagmandir also put down yet another rebellion in Gao.
Mansa Musa’s crowning achievement was his famous pilgrimage to Mecca, which started in 1324 and concluded with his return in 1326.
Accounts of how many people and how much gold he spent vary. All of them agree it was a very large group (the mansa kept a personal guard of some 500 men), and he gave out so many alms and bought so many things that gold’s value in Egypt and the Near East depreciated for 12 years. When he passed through Cairo, historian al-Maqurizi noted "the members of his entourage proceeded to buy Turkish and Ethiopian slave girls, singing girls and garments, so that the rate of the gold dinar fell by six dirhams."
Musa was so generous that he ran out of money and had to take out a loan to be able to afford the journey home. Musa's hajj, and especially his gold, caught the attention of both the Islamic and Christian worlds. Consequently, the name of Mali and Timbuktu appeared on fourteenth century world maps.
While on the hajj, he met the Andalusian poet and architect Es-Saheli. Mansa Musa brought the architect back to Mali to beautify some of the cities. Mosques were built in Gao and Timbuktu along with impressive palaces also built in Timbuktu. By the time of his death in 1337, Mali had control over Taghazza, a salt producing area in the north, which further strengthened its treasury.
Mansa Musa was succeeded by his son, Maghan I. Mansa Maghan I spent wastefully and was the first lackluster emperor since Khalifa. But the Mali Empire built by his predecessors was too strong for even his misrule and passed intact to Musa’s brother, Souleyman in 1341.