I can't speak to Mussk's innate intelligence. I can say he's mentally unstable and dysfunctional. He's incapable of performing basic tasks. He is completely unaware of his own limitations. He's a conman playing the same routine over and over again. He's doing to the US what he did to twitter, and he's highly irrational and uneducated about what he's doing.
Here he is in 1998. Back then he was at least able to sound normal and speak coherently.
here he is last week, unable to form a sentence
Perhaps he once was smart but he's no more intelligent than the average person. However he was fortunate enough to find an equally narcissistic person, one who similarly lacked a moral compass, and who happened to be running for president and who craved Mussk's money. End of. His money provides him an illusion and a way to maneuver with simply using it as brute force that others cannot and/or wouldn't do.