Did he simply post a photo or did he assert that he actually encountered the wolf at the location where the wolf was depicted? This is an important distinction the article does not address.
Posting the very realistic fake without saying it’s a fake (or indicating it’s a fake in some obvious way) is as good as saying it’s the truth.
It’s unreasonable to expect authorities to spend time carefully vetting every single picture in a time constrained situation. So they are vulnerable to exactly this kind of thing. And whether the guy intended harm or not, he did harm.