They're being charged with operating a service. Which they may very well have done. It sounds like they were at least running the front end user interface stuff, and that might be enough.
But what makes it interesting is that the real core parts of the whole system were (and still are) autonomous. Those contracts could (and still can) be used without them doing anything at all. So they were not operating those. And it's not so obvious that there is any settled law that applies to those core contracts.
Will you support the UK if they ask for the extradition of Signal developers, on the basis that say Signal will continue to have UK users accessing their service?
Where are your values?
You can - by not being inside the US, doing proper KYC and rejecting US customers.
I’m a privacy advocate, who thinks kyc laws have gone too far. But if you knowingly break a law you can’t cite the unjustness of that law unless you are engaged in an act of civil disobedience. Profits will suffer is not civil disobedience.