I think Meta's goals are becoming clearer: they want to make VR unbeliavable. Judging by this and by SAM, they want an AI system than can understand the world around itself in real time.
People do seem to vastly under estimate the time span over which Zuckerberg thinks and the end state he is going for. His vision is for a Facebook-like ubiquity of the tech. He sees AI as the pathway there because it means he can remove so many of the hardware sensors he otherwise would need that will be barriers to get the cost low enough. This is how he will make a little bit of money each from literally billions of users the way he has with Facebook. At this stage of development, he just needs these AI problems solved however that happens, whether it's internal or external. Releasing the tech only accelerates his broader version.