The clear pattern from 1985 to 2005 or so was that every new platform that came along experienced growth for a while and then decline and people involved in such platforms just moved on to whatever new thing replaced the old.
By 2015 Facebook had broken this pattern, and I thought a lot about why, not least was the explanation that Facebook was buying competitors (WhatsApp) and intimidating VCs to discourage competitors (otherwise having to pay $15 billion every few years to buy the next thing would seem like extortion)
Zuckerberg's fanaticism for VR is attributed to the belief that Facebook has a shelf life and they'd better be leading in the next platform.
Now I see it as "normcore people don't want to move away from old platforms and move to the next thing" and that what keeps Facebook alive is that if you want to keep in touch with: (1) your normcore friends and family and (2) community organizations you're stuck with Facebook.