“His name is already on the image where he signed it.”
With every “Save Image As” → “Share” cycle the picture quality tends to degrade. Sooner or later the signature becomes illegible or simply cropped out. Just look at the image quality difference now, after only being one day old!
Moreover, few people click a link to the source to check out the artist. But, even fewer read the signature, search for the name, and start browsing from there. Let alone the hassle of reverse image searching.
His name is already on the image where he signed it.