In my opinion, the technical know-how of Zuck was perfectly valid to build Facebook, but not this. VR/AR/anything with real-time world simulation and rendering is completely different from the web tech stack and could be considered to be a different world, with a different mindset.
Carmack obviously had the appropriate mindset, but AFAIK not the power to act. So Suck and his appointed staff probably took critical technical decisions regarding the software architecture of this project.
Given that we know that part of plan was to buy Unity back in 2015 and build their Metaverse on top of this engine, I seriously doubt this team really understood what they were doing.