We may not be able to say for certain, but Google’s massive influence is by far the most plausible explanation I can think of. And if the first step in your decision making is looking at what Google is doing, then ‘following marching orders’ is suddenly not such a bad description. (One can argue that with 3 % market share they don’t have much choice, but that’s beside the point.)
Why? AV1 was developed as a video codec. That doesn’t imply it’s as good of an image format nor that everyone who supported its development has vested interest in making it into one. Just because someone has made a cool hammer doesn’t imply they now need to view everything as nails. (This provenance even brings some drawbacks with it, yet this time seemingly no one took a pause before tossing in yet another image format.)
> Their hope was to use the existence of AVIF as leverage to give hardware vendors more incentive to provide hardware support for AV1.
This is the first time I’m reading about this and I’m having a hard time seeing how decoding images would make for a significant incentive to provide hardware support (especially when everyone was already more or less on board with AV1 as a video codec). But I could be wrong, of course. If you can provide any links where Mozilla gives this reason for adopting AVIF or any hardware vendor gives significant consideration to decoding AVIF in hardware, it would be much appreciated.
The way I read it, both companies were tentatively interested until Google said they changed their mind, and shortly after Mozilla decided they didn’t really care. Correlation doesn’t imply causality, but their positions followed a somewhat similar trajectory at the very least. (In contrast with, say, Apple.)
I just don’t see where you keep getting the idea that Google was at some point far more supportive of JPEG XL adoption than Mozilla was.
This wasn't the case. Mozilla even used similar wording as Google did.
Mozilla >We might find it necessary to support the format if usage becomes more widespread, but that will be a product decision
Google >There is not enough interest from the entire ecosystem to continue experimenting with JPEG XL
(this was retarded too, but wcyd if you are forced to say this)