I don’t know what a .webp file is but I don’t like it. They’re like a filthy prank version of the image/gif you’re looking for. They make you jump through all these hoops to find the original versions of the files that you can actually do anything with.
Edit: honestly I assumed it had something to do with Google protecting themselves from image piracy shit
You cannot rename a file from webp to jpg, but you can change the URL to .jpg and it will likely serve you the jpeg version. You can also convert webp to another format with dwebp or MS Paint.