>>105673031
I already said PEBCAK and it's not like I'm alone in thinking this. The dev team at GIMP recently tard proofed the webp export option when it detects that using lossy will result in a higher file size and worse quality if the lossy encoder is used instead of the lossless one.
Go ahead and give it a spin, attempt to save the PNG at
>>105672647 with a webp lossy parameter of quality 80 in the webp export option. GIMP will detect that you're being a fucking retard and save it to a lossless webp file.