>>718084000
They were "rich" because they had lot of gold in their soil, not because of civilizational advancement.
Their geographical isolation meant that they could never use that lucky gold to really modernize their shithole.
Mali was literally unknown to the outside world until Mansa Musa decided to go on hajj to Mecca.
Crossing the entire Sahara desert was something barely anyone would ever do in that era.
The "trade routes" mainly consisted in rare and occasional caravans forming a "chain", with each going from a specific point to another point, trading the merchandise and turning back. Goods crossed the whole desert, but people did not.
So when Mansa Musa arrived to Egypt, his shithole was still unkown.
He dropped gold left and right and myths started to form about his Wakanda.
Pretty much everything we "known" about the Mali Empire comes from a dude named Al-Umari who gathered the testimonies of Egyptian officials who had heard the testimonies of Mansa Musa's men during his visit.
Basically just a bunch of exaggerated and dubious hearsays that went though a chain of oral retellings.
After that Mansa Musa went back to his shithole and never travelled outside of Mali again.