For someone to actually stole your content, they would have to remove the content from your wiki and then move it somewhere else. That's what stolen means. That would be wrong. But your content was not taken away. It's on your wiki where every French fan can enjoy it.
To be honest, I'm surprised that you take all of this in the wrong way. The fact that someone wants to copy you it's a testament of quality work. Many of the stuff (like templates, codes, etc) that we did on my wiki was copied on many other wiki because our wiki was very popular. That's make me happy because it's a recognition of a good work that people want to emulate. If you write a book and someone offers to translate it in another language, would you respond with "how dare you!" or "Yes, please"?
And again, I want to stress that we are talking about a wiki in a different language. If someone copied your content and opened a French wiki, THAN I would understand and agree with you. While still technically allowed, that would be just counterproductive for both wikis and that's the reason why Fandom tries to avoid these situation (which sadly happens, like for example with the Italian Tekken wikis). But this is a completely different case.