Wasn't that also basically one guy from the VLC/ffmpeg community that drove that effort? I think they got funding from Netflix to do it again on ARM after demonstrating the benefits on desktop.
For decoding, yes, dav1d. But for encoding, a lot more SIMD kernels in libaom/SVT-AV1 written by other people.
(And lots of kernel shared between decoding and encoding, of course)