Mansa Musa was one of the richest, if not THE richest, man in the history of the world. He was the king of Mali, which is pretty much the closest the world has ever had to a real-life El Dorado. Gold was literally everywhere in Mali. By the end of the 14th century, in fact, over two-thirds of all the gold in Europe came from the kingdom of Mali.
Now, back to Cairo. At the time, the Egyptian capital was fabulously wealthy, and had the world's largest gold market. When Mansa Musa showed up, he brought with him around 60,000 companions and 12,000 slaves, all of whom were carrying four pounds of gold each. In addition to that, he brought with him eighty camels, each carrying three hundred pounds of gold.
Assuming these numbers are exactly accurate (they are just a ballpark figure given by scholars), Mansa Musa brought into Cairo-- the largest gold market in the world--- 312,000 pounds of gold.
In today's money, Mansa Musa walked into Cairo carrying roughly five and a half billion dollars.
Now, this is more gold than Cairo had ever seen. And the answer to your question of who ended up with the gold is this: Everyone.
Mansa Musa appears to have been extremely generous, and he freely gave out gold to pretty much everyone that crossed his path. He gifted beggars huge blocks of solid gold, and paid at random bazaars with fistfuls of gold dust. He even had a mosque built specifically for him to pray every Friday. No, I don't mean that he had a mosque built so that he could go in and pray every Friday. I mean that he would have a different mosque built every week for him to go and pray on Fridays.
Altogether, it's estimated that Mansa Musa spent 71,000 pounds of gold. The problem here will be clear to any economist: If everyone has gold, then no one has gold. The incredible and sudden influx of riches cause hyperinflation the likes of which has never quite been seen, and caused gold to become worthless. Like I said before, Cairo was the world's largest gold market at the time. By making gold worthless, Cairo's economy was plunged into very, very dark times.
It is possible that Mansa Musa's intentions were good, and that he was just way, way, way too generous. However, I'm not sure I buy it. He was a shrewd ruler and single-handedly put Africa in the map (literally--- check out the Catalan Atlas). I think an argument could be made that Mansa Musa was, in fact, quite aware of the effect his gold would have, and he traveled to the greatest gold market in the world; who were, in effect, his direct competitors, with the intention of weakening them while ensuring that Mali would not be affected by the potential issue of hyperinflation.