Assuming that USA Today did a good job in calculating all these net worths in constant USD, there is still a problem with this comparison that the article acknowledges to some degree. Most of wealth of the top four on the list was their land: illiquid; the value thereof varied considerably over time; the land was their source of income, but an income that would have been very variable; the land would have been used as security for short- and medium-term investing/speculating (often in western land), one source of the debts the article mentioned.
Another issue with the article is that it could have distinguished better among wealth acquired as a consequence of having been POTUS, as a consequence of having been in other high political offices, and as a consequence of non-government activities. It points out the sources of wealth, but a more informative list would have been subdivided among those categories. E.G.: Washington, Jackson, FDR and JFK inherited and/or married into wealth; Hoover was a mining engineer by profession, and made much of his wealth through that profession (salaries and investments); LBJ and WJC made their wealth as a consequence of their political power (both) and having been POTUS (WJC).
I’m mildly surprised, given Ds’ howling at the speaker’s fees he earned after being POTUS and given his wealth prior to going into politics, that Ronald Reagan didn’t make the “Top 10”. I didn’t see a link in the article to a complete list for all historic POTUSes, so I suppose it is possible that Reagan might have been #11 or #12.