Re: they already have the best on staff...
No, this is a way of announcing to the global marketplace that the US cloud is "safe" to do business with despite various state actors doing their best to intercept traffic and gather data.
In other words, the more evidence that comes out that the govt agencies are in everyone's business --and it seems to be getting worse, not better-- the more global companies will pull out of the cloud, which of course is commercially lethal for Goog/Amazon/Azure etc. So, Google are trying to reassure their customer base by appearing to race to close down 0-days before the NSA and friends can exploit them.
Nice of them to do it, but let's not assume that it's pure altruism: the survival of their business is as stake. I wouldn't be surprised if we see an industry alliance forming to share 0-days amongst the big cloud players. (Of course, how long after that before the NSA start running humint infiltration ops against researchers working for those companies? OK, I'll get my tinfoil hat.)