The site wasn’t ranking in the top positions and had no visibility. I decided to simply move it to another domain. I just copied the files and DB via ISP Manager. On another domain from a GoDaddy auction, the exact same site started ranking at the top.
The reason? Google randomness.
And an interesting detail: on the previous site, a link had a positive impact. So now two completely identical sites exist with the exact same content and design. I figure Google should drop one of them due to duplicate content. That’s my experiment—we’ll see.