A little extra context:

Dav1d was the surprisingly fast assembly implementation of AV1 decoding. Even for something in hand-coded platform-specific-assembly I think the general impression was that they'd done amazing work to really chase down every last bit of potential performance.

It didn't initially exist when AV1 was first rolled out and its arrival was a step change in powering adoption on devices without hardware decoding.

Dav2d is likely to play a similar role, but it exists from the start and can build on the work of dav1d, so should have an even bigger effect.

In a weird reverse chicken and egg scenario, having really good software decode that can be deployed will spur on hardware development and adoption due to network effects.