That still sounds like reading 400+ pages of Ran

Anthem is closer to 100 pages, and it's much more enjoyable than the ~50 pages of John Galt's monologue.

If you really want a shorter version of Atlas Shrugged, read a summary. Galt's speech is really long, pretty repetitive, and not that interesting, and it's basically just Ayn Rand getting off on her own ideas. There are much shorter summaries of Rand's ideology.

Elon Musk might be a close contemporary example of Galt

You obviously didn't read the book, because Galt actually innovated (book describes essentially a perpetual motion electrical generator). Musk is a salesperson who is particularly good at getting funding, as well as hiring people who know what they're doing. If Galt were real, I think he'd criticize Musk for the same reason you are, that he's only wealthy because of handouts from other people. Galt is also a philosopher (hence his massive monologue), whereas Musk doesn't seem to have anything resembling a philosophy other than "get rich by stroking rich peoples' egos."

he puts all his energy into destroying those structures

Then you've completely missed the point, or at least didn't finish the book.

The only things the MCs in the book destroy are their own creations, they never destroy anything of anyone else's (and that's critically important to Rand's Objectivism ideology). They're labeled as destroying public goods because the government sees all private creations as some form of "public good," but they merely practiced the ultimate form of "take their ball and go home," and merely exiting the market led to systemic collapse. The government collapses after becoming a dictatorship and due to its own failings, not because of any action from Galt et al. If you'll notice, they have exited society long before the government actually collapses, and the government gets more and more desparate (i.e. more authoritarian) the more people exit society.

The closest thing Galt does to "destruction" is hacking into a national radio broadcast to deliver his speech. That's it, he uses no force, and he is actually arrested by the authorities and they try to force him to lead the economic recovery, which he refuses to do. If he had "main character syndrome," surely he would've accepted that offer, no?

There's a reason he disappeared into obscurity, and it's precisely because he doesn't think anyone should be the main character. That's the entire point of the "Who is John Galt?" theme, he doesn't want people to look up to him, he wants to live on his own terms and be judged by his own merits, and only people who are truly interested will follow his example (again, not to follow him, but to follow their own self-interests).

And that's a large part of why I think the monologue is the wrong place to look for a summary of Rand's ideas, because it's pretty much the only time John Galt goes into public, and he only does it to spread a message, not to elevate himself. If that's all you read, it's pretty easy to assume than John Galt is some kind of important figurehead, when he's actually just the first in a larger group to exit a corrupted society.

Anthem is a much better distillation of her ideas IMO, and it's much simpler. Basically, it's a 1984 society where the government is stifling innovation merely to maintain consistent jobs. The MC writes by candlelight throughout the book, and in the end rediscovers electricity, which the ruling party has apparently hidden because it killed the candlemaking jobs. It gets a little campy with the couple rediscovering the word "I" and their own individuality, but the message is pretty clear IMO.