I don't think that's the entire story. Google actively pushed WebP, for example recommending it to webmasters in their page speed evaluation tools (and site per

I don't think that's the entire story. Google actively pushed WebP, for example recommending it to webmasters in their page speed evaluation tools (and site performance, as judged by Google, is a factor in your search ranking). If they invested the same resources into improving and promoting JPEG XL, we'd be using JPEG XL. I'm not saying the outcome is objectively worse, but ultimately, they did pick the winner here.