To remove previous guest ratings and reviews from your trivago hotel profile, you’ll need to contact the specific booking sites where guests made their reservations.
Why? Because trivago is a hotel metasearch, not a booking site or a review site.
trivago displays ratings and reviews as it does for rates; by aggregating information from third-party sources.
This means that once the various booking and review sites have removed ratings for your property under the previous management, the changes will be reflected accordingly on your trivago profile’s Ratings page.