So why the change of heart? Well, it's not. They are simply not able to compete anywhere on the Pareto frontier. So they give their relatively bad stuff away and play the high and mighty game, because that's all they can do to get returns.
Not a great look – and I would expect that to last about as long as they can't actually monetize their stuff more effectively.
Is this actually true? They have their closed social graph or whatever but come to think of it they're built on a lot of open tech, the web, Android, etc. Maybe they don't contribute back to a lot of these things?
I'm fully ready to believe it but it would be interesting to dive into this conjecture.
React was already quite prominent in web technologies, but that license pointed a loaded gun at any business smaller than Facebook who wanted to use React. They opened it up to its current license, MIT, as the backlash built.