Let's say German court rules that X cannot operate in Germany. X decides to shut down any brick&mortar locations in Germany including any data centers located in Germany, but they do not stop Germans from accessing a public web service located outside Germany. What's the point? Will they then go after Germans continuing to use X?
In other words, a German court ruling against a non-German company can only go so far. However, IANAL, so willing to learn how a German court ruling would be anything other than a nuisance to a non-German company
X's website was blocked, and then the courts looked at how Musk operates his business interests and decided that Starlink was a valid recipient of the penalty fines, and Musk gave in.
Also, ignoring the court order would be a possible violation of the DSA, which can be fined at 6% of a company's global turnover.
Musk may put himself in a rather awkward position, as the CEO of a company actively refusing court orders. He may be arrested and prosecuted for his actions, so it'd be unwise for him personally to visit his European offices. I'm sure he has committed some form of crime throughout the past couple of years they can jail him by.
In practice, we'd probably just see a short-lived domain block. Jailing Elon will probably set off Trump and his cronies so the EU will probably not bother to go after him.
No need to, he could simply be bounced at the border.
Some edgy kids may use a VPN or something to bypass the ban, but 95% of people will simply move on to the next usable thing.
Another route is to tell financial institutions that payments to X must not be processed. That will immediately shut down advertising revenue from German companies, which will mean Germans will become less profitable users for X.
So... Yeah, Twitter may flout the ban, some users too, but most users and, more importantly, German banks won't.
The point is that Twitter makes money by advertising, and if they can't operate in Germany, they can't do business with German companies that want to use it to advertise. So it stops making money.
And if he doesn't comply, and continues doing so, contrary to court orders, they can also put injunctions against Starlink, start seizing Tesla assets, etc.
In the case of SpaceX, it would be even less feasible in that it’s a major DoD provider and there are defense treaties between the US and EU member states.