He exposed criminals illegally spying on US people at home, and lying about it to congress. They were doing nothing less than building the infrastructure of a turn key police state.
He had zero chance of being a whistleblower. He saw precisely what happened when William Binney tried that just a few years before. Binney went to the DOD IGs office to report wrongdoing. He also went to the House intelligence committee.
This resulted in being raided by a dozen FBI agents at gunpoint who yanked him out of the shower. The same raid was launched against two co-workers who went to the IG with him. A staffer for the House intelligence committee was also raided.
His security clearance was revoked, and he lost the ability to work in his field. Snowden saw exactly what happened to whistleblowers who follow the prescribed route. So he wisely found another route to expose America’s budding Stasi.
Very good summary of the historical facts man. How soon we forget how serious this situation truly was indeed. And they are STILL doing it with the support of the brainwashed sheep.