Because I know that's what we'd all do when fleeing our home country with a couple million highly desirable classified documents, attempting to avoid prosecution.

We'd all make sure to "protect" ourselves from "leverage" by the people who might (and ultimately did) help us achieve our goals by destroying our one and only bargaining chip.

His autobiography is worth reading. Yes, he wrote it, so it can be skewed all kinds of whichways to suit his agenda, but the picture it paints is of someone born into the US establishment (government / military / intelligence) and essentially a strong belief in the outward impression the US presents to the world. Freedom and Liberty!

I may be all kinds of naive in saying this, but I think he did it for relatively purely "the US must be better than this" motivations. I can't see his motivation being of the same ilk as The Cambridge Five.

People with ordinary levels of moral weakness would never become whistleblowers in the first place. They'd keep their excellent, comfortable and stimulating government careers.