I'm surprised at how many people are going "well, people always thought Google would be a Search company!"
Google hasn't made many multi-billion dollar deals for something that seems like nothing. The closest would be Motorola, but even that was more for patents (which didn't end up worth anything.)
OR, which was sold for shockingly close to Motorola, has a fraction of the employees (all of which now have financial incentive to leave as soon as their shares vest), has never released anything, and is working in a field where there's no real differentiator that makes them special. The only single thing I can think of that makes them different than whomever jumps into VR next is that they did it first.
First mover advantage is a real thing, but not a $2 billion thing. I really fail to see why Facebook couldn't do what OR did and hire 10 people do make this product for them for 1/20th the cost. Other than the obvious, that the type of people that want VR headsets is currently a niche group that overlaps strongly with the type of people that would actively avoid buying a FB product if an alternative exists.