It's hard to compare people who lived under vastly different economic systems. I would also put people who were the leaders of their country into a different category: the line between what they own and what is part of the nation's wealth is very blurry. I think even for more recent private individuals like the Carnegies it's a little more complicated than taking assets multiplied by inflation rates. Spending power also comes into it, and you could use another measure like net worth as a % of GDP.

Musk may still fall short in those ways, which is why I made the "ever" a question. Poking around the internet a bit more-- your link & others-- it seems pretty likely. Then again I'm not sure there can really be a meaningful difference in wealth between anyone who was worth the equivalent of > $100B in todays money, however it's calculated. (Possibly you'd distinguish between money on paper vs. more tangible assets. Or some method of distinguishing Musk's wealth, a lot of which seems based on the speculative future value of Tesla than based in its current operations)

Yes, that article is doing some really weird comparisons. JD Rockfeller's net worth was no higher than $24B in modern inflation-adjusted dollars, but the article claims more than 10x that figure.