You may try one of the following to make the thumbnail images of WebP files are shown on File Explorer as below.
WebP Image Extensions offered by Microsoft enables you to view the thumbnail images of WebP files on File Explorer. You may visit the link below to get WebP Image Extensions from Microsoft Store.
Honeyview also enables you to view the thumbnail images of WebP files on File Explorer. If the problem persists even after you have installed the app, however, you may try the following steps.
Open Registry Editor and delete the following key.
This key is used for processing thumbnail images, and the problem may occur if the key does not work correctly.
Uninstall Honeyview, then download the latest version of the app and reinstall it.