My definition of cheating is when someone creates fake accounts to create fraudulent votes on a submission.
I manually went through all of their ratings, and I don't see any evidence of that. It's very likely that they have access to a lot of distinct people (their friends) who were willing to go and create itch.io accounts and vote on their entry.
That's not cheating, but a disadvantage of public voting system. Many other submissions did the same exact thing, they just were the ones who happened to have the most friends.