>probably in favour of WebP

I think it would be avif. WebP can't compete with jpeg-xl in terms of feature set. But compared to avif, jpeg-xl allows seamless transition to jpeg (for compatibility), progressive decode, higher bit depth HDR, and ability to use common encode/decode pathways with jpeg.

That would have been seen when it would be properly supported by browsers. Chrome pushed webp support and made it commonplace across net, even though it finds no usage elsewhere. JPEG-XL to be fair took a significant time in development, but axing it in the monopoly browser means that any chance of adoption on web is fairly slim, and that would affect further adoption even if it is used in other cases, such as smartphone images (android is also google though)

opera is also based on chromium. Basically, its just reskinned chrome with opera's proxy and vpn thrown in the mix

Reason for deprecation could entirely be docile, but given the recent events, my first instinct was to conclude that it must be to benefit competing standards where google is involved in development