Snowden (and the world) would have been much better off if the only thing he took with him was about the illegal domestic spying, but of course he didn't have the time to analyze the data, he just took it all and ran and let journalists publish parts of it. Because some of the data was about legitimate US intelligence work overseas, people could accuse him of harming US interests on top of whistleblowing.

Some people got their information about Snowden from a "news source" that told them "this traitor / Russian spy leaked the details of the US intelligence work overseas", and did not tell them about the warrantless domestic wiretapping.