I loaded the page with Firefox 65 beta and all the images worked for me. The site doesn't seem to be serving WebP images to Firefox. When I checked all the image types via Page Info they were mostly JPEGs with some PNGs and one SVG image.
There's probably some other reason why the site is broken for you. Have you perhaps changed your browser's user agent string and so the site is giving you WebP images because it thinks they will work?