There was an interesting email from Zuck released during one of their trials where he explained why they were focused on VR: it was basically all about Apple and wanting to own the next platform.
Makes sense although gaming is and will remain the most significant use case for VR in the foreseeable future
The original email is from 2015, posted on HN in 2022: https://news.ycombinator.com/item?id=33538742#33540359