* They did not own all of the copyrights at the time the suit was filed. In fact, they may not own the rights now.
* International treaties like the Berne Convention have means to resolve these disputes. The plaintiffs have ignored those and filed suit in their own, likely incorrect, jurisdiction.
* The suit, and the decision, does not ask for the texts in question be blocked in German jurisdiction. It calls for them to be taken down entirely, even though they are legal in the US.
I'm sure Disney wouldn't be happy either if their movies that are still under copyright in the US were to be published for everyone to download on a server in some country that had shorter copyright than US. They'd try to sue as well.
Disney could also apply legal sanctions to the owners of the servers, should they ever travel to the US, and could probably convince the US Marines to extradite the owner. But I don't think that should be encouraged.