I was a huge SpaceX fan from the early days so watched a lot of Musks presentations and interviews and noticed a lot of repetition and always felt he was strongly working from talking points combined with a reasonably good high level understanding of the topic.
He didn't work as well off script and seemed to have stunted emotional development, not unlike a lot of internet age manboys raised on memes, video games and porn. It is difficult to reconcile his behaviour with an adult, father and manager of people and money. I suspect he has some seriously competent peiple around him like Shotwell who cover for his fuck ups.
IMO he probably is the kind of guy who can soak up stuff around him, turn it into a set of talking points and repeat it with the appearance of expertise. I think he may have had some cognitive decline due to age and lifestyle but I think he was a pretty competent bullshit artist in the past.
I am not an expert at anything but like many IT people discovered long ago that I can pick up most things in my general field with a bit of research. It is a dangerous mindset sometimes. There really is the feeling that with some basic undergrad math and comp sci and a weekend of googling you can understand quantum field theory and it's totally delusional of course.
Unfortunately the fake it to you make it culture seems to have won. It doesn't matter how crap you are, if you put yourself out there with confidence you will outcompete the quiet competent types. And when you get caught out there never seem to be consequences.
