AR/VR was always a side project for Zuck (like the Aquila airplane or the Libra cryptocurrency or AGI) that he works on because he's bored. It was pretty clear from the product's popularity and Metaverse experience that it didn't have any legs. Carmack had little to do with that one way or the other, and the Apple Vision pro shows that it's not an execution or quality issue, it's product-market fit.