Never get confused about what hes doing. He is not giving it to the world, he's trying to ensure that the competitors have no proprietary advantage that can overcome network effects. They have some other plan to monetize it, and seeing as it's Meta, I'd be willing to bet it's predatory.
It's similar reasoning to Meta being the largest contributor to OSM. Google already has the commercial advantage on maps, and that's the key difference, but if OSM can beat Google on accuracy then they're not a monopoly player anymore.
Make no mistake, his goal is to beat Google and take their position in the tech industry.