Who became a powerful center of learning and a center for Islamic religion

Mansa Musa's

After his return from Mecca, Mansa Musa began to revitalize cities in his kingdom. He built mosques and large public buildings in cities like Gao and, most famously, Timbuktu. Timbuktu became a major Islamic university center during the 14th century due to Mansa Musa's developments.

Explanation:

i believe the answer is: returns on investments, no wages

people who belong in upper class society would most likely get there by obtaining multiple source of income, which a certain percentage of ownership for businesses. since most of them are job creator, they would most likely get their money from profit, not wages.