If you make a martyr out of Snowden you'll bring a lot of negative attention to the issue of mass-surveillance. So the best outcome from the USG's perspective is for Snowden to go through some level of punishment that will act as a deterrent for other would-be whistle-blowers while not rustling the feathers of anti mass-surveillance proponents.

Makes you wonder, does the USG feel a sense of relief now that all this mass-surveillance stuff is out there and the general public doesn't care that much?