Snowden did not release these documents, he doesn't cherry pick what things is worthy for the US public to know. He handed the documents over to journalists a long time ago and left it entirely up to them which of them to release. The only thing he decided for himself was to make sure that no personal information (about field agents, colleagues, etc.) gets leaked, and he did so by not grabbing these kind of documents.
It seems to me that you have never watched a Snowden interview or chose to ignore the reasons he gives why he did what he thought he had to do. The NSA's and GHCHQ's mass surveillance is so pervasive that it seriously endangers society in the long run. The same could probably be said about other agencies, but he happened to be a contractor for the NSA and stumbled across *their* problem. Apart from the fact that it is completely obvious that the NSA is collecting more information than Google, because they have access to Google like everybody else, we already know fairly well which information Google is collecting but did not know how and still don't know sufficiently well how much the NSA is collecting. Snowden has made it clear that he wanted to start a public debate about the relation of this pervasive data collection to the US constitution. He's not against the work of the NSA. (On a side note, it is also not such a bad idea to think about whether it is a good idea that private companies can collect so much data about us, isn't it? If Google offered a special paid data information service, say, for politicians to provide them with extra information on the private surfing habits of their political adversaries, would you agree with that?)
You might disagree with his assessment of the situation, of course, but do not forget that this is not a matter of mere personal or political opinion just because it concerns our future. Whether is assessment is right or wrong hinges mostly on factual matters. And then there is also the question of what you would have done if you had come to the same conclusion as he, and for which motives you would have acted. Some people trust in authority and chain of command more than others - a standard defense in the military although I don't want to invoke 'Godwin's Law' here. Others give more weight to acting according to what they have come to believe after they have carefully studied the evidence.