I think Musk is a con artist, but why is it difficult to wrap your head around a person benefiting less from his billions than the society? Society gets to use these billions in many ways more than the person himself. Society gets the products made by the businesses that are valued at billions, society gets the jobs and paychecks from all of this money. What does the person get except for a headache of dealing with the norms and rules and taxes imposed by the society upon his business? He really doesn't eat much more than the next guy, though his meals will be more expensive because they are cooked by some private chefs. But the cost of the food, chefs, housing, airplanes, whatever is negligible compared to the value of the company that society gets to enjoy. Even just the trading of the stock market allows people to have something to invest into, there are jobs, there are products, then there are various contracts required to maintain this business, so there are other side businesses that rely on the gigantic companies owned by the billionaire.
Again, a billionaire personally can use maybe a few hundred million dollars, maybe even a couple of billion (if he buys a couple of yachts and a few mansions). The gain to the guy is completely negligible compared to the gain to the society. It is like infrastructure in itself, that's what these huge businesses are. To say that this is 'Libertarian-Randian gobbledygook' is simply to use a personal attack in place of an argument.
But again, I am fully convinced Musk is a gigantic fraud, running his empire almost exclusively on vaporware.