The people who do these eBook sales schemes (the equivalent in brick-and-mortar stores, what few remain is to send reps in to actually buy up all copies at a certain store) pay for reviews, they pay for people to trash and 1-star similar books by those they see as competitors. AI provides tools to a) support individual creativity in a way that means a person who might be doing this for $200 on Fivrr could conceivably use it to write their own work better; b) identify online ad/review abusers quickly and efficiently.