Eh, open-sourcing is just good business, the only reason every big tech company doesn't is that loads of executives are stuck in the past. Of course having random people on the internet do labor for you for free is something Google would want. They get the advantage of tens of thousands of extra eyes on their code pointing out potential security vulnerabilities and they can just put all the really shady shit in proprietary blobs like Google Play Services, they're getting the best of both worlds as far as they're concerned.

Large publicly-traded companies do not do anything for the good of anyone but themselves, they are literally Legally Obligated to make the most profitable decisions for themselves at all times. If they're open-sourcing things it's to make money, not because they were "good guys".