The "investigations" you reference were by German media, whereas the wsj article was allegedly from German authorities. Moreover, while you accuse the wsj article as "hearsay", the same is true for the tagesspiegel you linked. The crux of that article's claim is that the company that rented the yacht had Crimean owners with ties to Russia, but no proof was presented. We're asked to trust the journalists on that, just as we're asked to trust the wsj journalists on the facts of the German authorities' investigation.