Luxury hotels are more likely to post fake reviews than cheaper properties. That appears to be because people deciding on price are less influenced by reviews, while a decision to drop $500 or more per night on a resort will be influenced by more subjective and experiential elements of a stay.
It used to be that hotels would post fake negative reviews of competitors. But they’ve shifted away from that and more towards posting more fake positive reviews of their own properties, as Airbnb has grown.