This has nothing to do with privacy! Criminals have their techniques and methods to protect themselves and their “businesses” from discovery, both in the real world and in the online world. Even in a complete absence of privacy they would find a way to hide their stuff from the police - at least for a while.
In the real world, criminals (e.g. drug dealers) also use cars, so you could argue, that druck trafficking is a side effect of people having cars…
I think you are mixing here two different aspects of this and of similar past cases. I the past there was often a problem with takedowns of such sites, because german prosecutors did not regard themselves as being in charge of takedowns, if the servers were somewhere overseas. Their main focus was to get the admins and users of those sites and to get them into jail.
In this specific case they were observing this platform (together with prosecutors from other countries in an orchestrated operation) to gather as much data as possible about the structure, the payment flows, the admins and the users of this before moving into action and getting them arrested. The site was taken down meanwhile.
If you blow up and delete)such a darknet service immediately upon discovery, you may get rid of it (temporarily) but you might not catch many of the people behind it.
Okay, Orangeman! Now it’s getting personal…