Unfortunately it's not a question with a yes or no. For one, we really don't have a good estimate on how wealthy mansa musa really was. The earliest sources refer to his spending in Cairo to be so lavish that it completely devalued gold. We don't know exactly how much gold he was travelling with, some sources refer to him travelling with thousands of men, slaves as well as hundreds camels laden with pounds of gold and gifts. What we do know is that his wealth relative to Cairo was enough to accidentally crash their economy. However, it's worth noting that only egypt suffered this way, and at the time the economy was undergoing issues due to poorly minted, underweight coins. This is something that's very rarely brought up when talking about mansa musa but in general the mamluk economy tended to have issues relating to their currency. This was the case long after mansa musa was dead. We also know that he controlled much of the west African and saharan salt trade, in addition to existing gold mines. So not only did he have access to what was likely one of the largest gold sources in his part of the world but he also controlled valuable commodities(salt and ivory) that created a gold surplus in trade with other nations. Additionally his reign was documented as including many building projects, mosques and schools, which supports a large and flowing source of wealth and resources. So, while we can't say for certain that he was wealthiest man in history, it seems likely that he was by far the wealthiest man in his sphere of influence