I don't know how you're measuring "greatest" but I certainly consider his greatest accomplishments to be putting together, betting on, and operating the companies that produced these products. Of course he doesn't know how to build a Tesla batter or a SpaceX rocket himself - probably no one person does.

These were very difficult industries, industries that were extremely contrarian to bet on when he did. Making the financial bet alone would be a great accomplishment for any normal person. Peter Thiel is a famous investor for making far less contrarian and far less successful bets without operating anything except Paypal.

Musk's bets were far more concentrated, and he chose the personnel, operated the companies, made the strategic decisions, and yes, also marketed them brilliantly. But he only got to flex those marketing muscles because he spent a decade assembling, managing, and financing the teams that built the product in the first place.