Simple to explain: Some unimportant German politician from the left-wing party read some unpleasing information about him on the German Wikipedia. He claims that the information is not not true, but he wasn’t able to get it removed from the article. And as it would be too easy to notify someone from Wikipedia about it and let them lock the article, he decided to give it a shot at the court. Of course, he couldn’t do anything against Wikipedia itself, but he got the domain wikipedia.de closed down for a few hours. As the information was removed, the domain is going to be reopened very soon. That’s it.