Zuck and Co just completely failed to read the room. Horizons didn't fail because the technology wasn't ready - it failed because nobody actually wanted the product. It didn't solve any problem and added a ton of friction (headsets, eye goggles, no legs, etc). The headsets were uncomfortable and isolating. The vibes were creepy and weird.

The rolled it out like a cheesy corporate team-building mandatory exercise, not something where anyone would want to actually spend any time by choice.