Final answer:
Djenné and Timbuktu became major cities in West Africa not only due to commerce but also as centers of Islamic scholarship, with investments in educational institutions by rulers like Mansa Musa.
Step-by-step explanation:
In addition to being commercial centers, Djenné and Timbuktu became major cities in West Africa due to their roles as centers of Islamic scholarship and education. Sharing the same religion with many trans-Saharan traders, these cities strengthened ties between different groups and facilitated the exchange of commodities such as gold, salt, textiles, and more.
Notably, under the rule of the Malian Empire, Timbuktu and Djenné flourished with advancements in public works, including palaces, walled cities, and iconic mosques. The significance of these cities was further elevated when Mansa Musa supported the establishment of educational institutions, enhancing their status as hubs of Islamic learning.