Which format are you saying the Chromium team made and wants to push in favor of jxl?

All of that is pretty moot and not something I care about much as long as it's better than JPEG. Let everyone support AVIF and stop this perpetual bikeshedding.

AVIF already works in all browsers, all sites should support it.

I'm a big fan of JPEG XL, but even its most dedicated fans have given up the argument that it is the best for compression efficiency. AVIF's generational leap took place in August 2024 with Tune Still Picture in SVT-AV1-PSY, so much so that Google integrated it into their own encoder and has done very impressive work optimizing it further for the human visual system. JPEG XL's strongest quality is its featureset; lossless JPEG recompression, for example, is really incredible

My theory was that strategically, Google wants to make AVIF ubiquitous to promote adoption of decoders for it in mobile devices; AVIF losing to JXL is a "whatever" on Google's part, but AV1 losing to H265 means another decade of royalties for YouTube.

Existing tools really just need to do a better job keeping up.

What tools? Imagemagick handles avif fine converting to and from it. Gimp as well. There is also basic avifenc.