Facebook thinks about social networks in two dimensions:

1. Audience size (eg <50, <500, 1M+); and

2. Format (eg text, images, video, VR, AR).

You can go through the exercise of placing every social network on this grid and there are gaps. Implied in this is a progression in formats and we've certainly had that from text to images to video.

In this framework, the acquisition of Oculus makes more sense.

I personally question the premise that formats will evolve from into VR. VR seems to be viewed as a mere stepping stone to AR. I agree that AR seems more likely an outcome. I just don't see VR going mainstream in a way that FB seems to be betting on.

Disclaimer: Ex-Facebooker. Opinions are my own.