The simple truth is that he made electric cars viable competitors to gas-powered cars. His genius is not that he invented them, it's that he profitably manufactured decently reliable cars for a price that lots of people found attractive.
You can try and dismiss it as "marketing," but things like the Gigapress and FSD/Autopilot are impressive technical achievements in their own right. Even more impressive is that he built up a new car company that didn't fold and has had the best selling car in the US for significant chunks of time.
I don't like the guy, I think that FSD is dangerous, and I will never buy a Tesla for as long as he's in charge, but it's crazy that so many people feel the need to discredit his achievements. Sure, he benefited from selling carbon credits and EV subsidies, but if it were such an easy thing to do why did it take so long for anyone else to sell a good EV?