For what it's worth I don't think Elon Musk is particularly smart, but I'm also comparing him to myself and other people I respect... and some people try to tell me that I'm the smartest person they know (which I think is weird rather than a flex)... so maybe the bar is a little high (or not).

I am always very suspect of people equating having money with being intelligent.

Because it's a thing that happens very often and is complete bullshit.

As you've already pointed out here: people with very high IQs are often quite bad at managing others and their own finances. One of the smartest guys I know got audited by the IRS because he "just forgot" to pay his taxes. Most high IQ individuals are barely functional in certain regards (like losing their bus money because it's in the wrong pocket). It's a very narrow range of intelligence that doesn't account for all the other things a human brain needs to do.