I hear what you're saying but ... clearly SpaceX has made some broad technical decisions - I'm think of using metholox or making starship out of steel or falcon first stage re-usability - that seem to have been the correct choice.

I doubt Musk originated these idea but he was the one who ultimately made the decision on them. There were a lot of other people who had the same choice and either didn't come down that way or took a lot longer to come to the same place.

Like I said, genius? I personally wouldn't use that word. He's not an idiot though. He might be the minimum viable product for technical knowledge combined with a large amount of money but that's still pretty remarkable.