Musk is a billionaire doing billionaire things. Of course he's doing rocketry (just like Bezos) and of course he's playing Henry Ford doing car manufacturing. That's expected and not a surprise and the article expects us to be surprised by this.
If you expected most billionaires to get into rocketry, you would expect there to be hundreds or thousands of rocket companies given the more than 2000 billionaires around.
Not all of the NewSpace billionaires are working on launch vehicles (eg Bigelow). But probably several percent of billionaires in the US have space companies
Most billionaires don't get into rocketry, but exceptional wealth is a requirement. Other billionaires do other ego trips.
Yes, because that's what all billionaires do. Every single last one of them. Pretty pedestrian stuff.