Is there a way to prevent this from happening?
Not really. One can make it harder, but whatever is done, someone else can overcome that with a little effort. As you have seen with the modified logo. Watermarked logos are actually a good "prevention" method.
If you have notified Itch, that is pretty much all you can reasonably do. You could take some legal action, but this is usually very difficult, because of the location of the criminal. Maybe the account is even hacked and a few games are from the hacked developer.
The stolen game appears in search results higher, because Itch is very "relevant" in regards to games. It happens very often. Stolen games, often infected with malware, that are uploaded to Itch and appear within hours on the search engines.