Maybe in the tech community on Hacker News, but ask your mom if she knows who Elon Musk is. Then ask her about Steve Jobs and Bill Gates. My guess is that you get a no idea for the first.
If I asked my wife today, I'm certain she's knows Jobs and Gates, maybe Bezos (and that's a big maybe) but no way would she know who Musk is. Lets not mistake our echo chamber for the world.
The only people I'd expect a 30-40 year old "smart, but not tech industry" person to know are Steve Jobs, Bill Gates, and Mark Zuckerberg -- younger people wouldn't be as likely to know Bill Gates, except maybe for his philanthropy or due to references in classic rap music to "Bill Gates money". Sean Parker might be higher in the mass market than expected due to his colorful portrayal in the movie. Then probably Trump, Ellison, and Branson for their non-tech accomplishments (TV, racing/living, and airlines/music/etc.), and then probably rappers (Jay-Z, 50 Cent, etc. are all clearly entrepreneurs as much as musicians), and maybe Oprah.
The only person I'd expect everyone to know is Steve Jobs. I wonder if that will be true of people who are 5-10 years old today, in a decade.
I'd assume Musk is more popular than tech entrepreneurs overall due to rockets and cars; even in tech no one knows about Zip2 and "one of the many founders of PayPal" is kind of a stretch (outside HN/VC, who knows Keith Rabois or David Sacks?)
Even the most successful business/tech entrepreneurs are less famous than a B or C list media celebrity.
You'd be surprised. I've been hanging around here for a few years and I have no idea who he is. Although a little voice in the back of my mind says he might be the Dropbox guy.
In the startup world, more folks cite Zuckerberg and Dorsey. Hell, even Mason and Pincus get more press than Musk (though probably for the wrong reasons).