It wasn't killed off. Support was removed from Chrome, for what appears to be rather spurious reasons, but practically everyone else are busy implementing it.
While I'm not the biggest fan of WebP, using generation loss as a metric wouldn't be an indicator of a real world scenario. I can't think of any actual instance where an image needs to be re-encoded, say, 10 times, let alone 100+ times.
What do you think happens to images shared and re-shared between people online?
> killed off
my guesswork is that JPEG XL will likely outlive Chrome by 100+ years