"These Amazon vendors send to reviewers a list of items/products for which they would like a 5-star review. The people providing the ‘fake reviews’ will then buy the products, leaving a 5-star review on Amazon a few days after receiving their merchandise.
Upon completion, the provider of the fake review will send a message to the vendor containing a link to their Amazon profile, along with their PayPal details.
Once the Amazon vendor confirms all reviews have been completed, the reviewer will receive a refund through PayPal, keeping the items they bought for free as a form of payment."
https://www.safetydetectives.com/blog/amazon-reviews-leak-report/