This argument seems fallacious. Ignorance in one area doesn't automatically imply ignorance in another, just as intelligence in one area doesn't imply intelligence in another. You acknowledge this standard for yourself when you admit your lack of knowledge with regards to cars and rockets, yet you don't afford the same standard to Musk, who may well be reasonably intelligent with regards to one or both of those things.
@vacatio A person doesn't need to be a complete polymath in order to listen to experts. If someone is visibly and horrifically ignoring their highly paid experts in one area, I think it's reasonable to start questioning whether they're listening to experts in other areas.