Instead of seeing every positive review of a product as a great comment, look at it as a vote in a popularity contest. In addition, they didn't know if the customers they were targeting had recently interacted with the product, since they only sent their review emails on Mondays. Customer participation on review sites provides valuable information to help the company to constantly improve and adjust its products and services. Ask customers who bought you a review about a week after receiving their order (or later, if your customers aren't likely to use your products right away).
Including the possibility of uploading images and videos can increase the chances of getting an opinion, since people like to share multimedia content, especially if they particularly like a product.