Some CDNs like Akamai and Cloudflare have options to optimize images. We use the Akamai one where I work. It means our creative teams, customers, etc. don’t need to worry too much about whether an image is properly optimized when they upload it. Akamai will, behind the scenes optimize the quality, color palette, and image type (jpg, web, png, etc) and create a number of different versions of the images. Then when a client requests the image Akamai looks at the client device (mobile vs desktop, screen resolution, browser version, etc) and serves the copy of the image that’s best optimized for that device.

So even if the URL ends with .jpg you might be sent a .webp. If you use the browsers developer tool to inspect the response headers you’ll likely see the Content-Type header says it’s .webp as well.

Because the URL is lying, and the image is not a jpg.