Before Edward Snowden joined Daniel Ellsberg and Chelsea Manning in the annals of American whistleblowers, he was a young man who witnessed the attacks of September 11, 2001, and enthusiastically volunteered to join the national-security state. Back then, he believed in the wisdom of the War in Iraq, saw the National Security Agency as a force for good, and hoped to serve within the system.
Since his first interview with Glenn Greenwald and Laura Poitras, we've known that he gradually lost faith in the federal government, believed it to be engaged in illegal, immoral acts, and decided to gather and leak some of its secrets.
One of the most comprehensive narratives of what specifically prompted his transition from insider to conscientious objector appears in the recently published interview he granted to James Bamford, author of several books on the NSA. Whether one believes Snowden's leaks to be salutary or deeply regrettable, it's useful to understand and grapple with what prompted him to act as he did, especially as the Obama administration works to make future leaks less likely. One method for preventing leaks that hasn't been discussed: Run a federal government that carries out fewer morally and legally objectionable actions in secret.
According to the interview, Snowden was disillusioned and influenced by what he saw during his time at the CIA and the NSA, as many Americans would've been: