> Are there any previous examples of someone doing something similar to what Musk did and the punishments they received?
If you look at the facts of what Musk did...yes, there are literally hundreds if not thousands of examples, and they mostly go to jail or face, as Musk is, stiff civil penalties. It's pretty clearly fraud; he made false statements, which he knew or should have known were false, and he did so with the intention of manipulating his firm's share price. That's open and shut, and Musk hasn't really tried to deny it.
> compared to the slap on the wrist that many people were predicting.
If you squint a bit, there's a lot of reasons why what Musk did "feels" different. Maybe you think he had good intentions; maybe you think he was stressed. Maybe he was on medication that interfered with his cognitive abilities, maybe he's just a great guy, maybe the fact he wasn't financially profiting from the fraud makes it different, maybe Tesla is just really cool, maybe short sellers are just really unsympathetic, maybe this somehow just doesn't "count". All of those are plausible reasons why the SEC might give him at least a partial pass, and a lot of commenters were sort of expecting that it would happen.
But fundamentally, the legal system says that what he did actually is really bad. CEOs of public companies who lie about material events in order to manipulate their share price are committing a serious crime, which is why outside of penny stocks and scammers, they never do that. Even if they were tempted, their legal team would tackle them and sit on them until the urge to set their career and company on fire faded, and the legal team would have the opportunity to do that because other CEOs don't just tweet whatever occurs to them, in large part because they know that's super dangerous, because this exact thing could happen.
It's hard to overstate how unusual Tesla and Musk's behaviour here is for a multi-billion dollar company. Other companies of this size only communicate to investors through carefully vetted press releases, which is boring, but makes sure they don't accidentally step on a landmine. Tesla (or Musk) chose a different path, and here we are.