Makes sense. Maybe smut pumped up the ratings. Because it would be funny if someone made 30 accounts to give themselves ratings
No, it's not smut, and I doubt there are a lot of authors who will make 30 accounts just to make 30 5-star ratings. Especially considering how there are anti-cheat systems, and they might lose those ratings.
The main reason for the extremely skewed rating, in my opinion, is that readers think that 5-star ratings help the novel. They think it helps the author, some readers who rate 5-stars are authors, so they give high ratings as an acknowledgment of an author's hard work and encouragement. Some readers give 5-stars simply because they really liked the novel, but all of it is a part of the problem. Because usually, those readers and authors who rate other stories don't rate the novel 1-star even if they disliked it. It's frowned upon and seen as a dick move. Why would you ruin the mood of an author who worked hard to splurge some words? Because of that, almost every novel has an average rating of 4 and higher. The novels that don't have such a rating are either really bad or very controversial.
