Intelligence isn't measured strictly by success. I know people who went to MIT and majored in mathematics and engineering, I know people who got 1600 on the SATs, etc.
Some of the most successful business people I know aren't really smart, they just know how to run businesses successfully. For example one of the weathier people in my area run a construction company. They leveraged that into also running plumbing company, gas company, septic company, etc. so when you build a house they do it all themselves or more accurately, sub the work out to themselves. THey turned their money into other successful bsuiness ventures and own tons of land and rent out tons of business properties. Again the people who run this aren't the smartest people I know but they're hard workers and make good business choices.
The smart people I know grew up poor to middle class and didn't have a safety net if things fail. Musk, Gates, Zuckerberg, etc. could swing big because if they failed they wouldn't fall into poverty.
Add in the bit about being right place right time. Musk if he was 10 years older couldn't have done things the way he did. If he was born a decade earlier the same. Would he have been successful? Probably because again, wealthy. He had a safety net had he failed. Most truly rich people are that way. Sure some exist that aren't. But they were able to do things that poor people weren't.
He has an IQ of 150 or higher. Considering that represents .04% of the population, it's extremely unlikely you know a dozen people smarter than him.