Snowden is really clever with these interviews. Right away in the interview he establishes his concerns about the government, then briefly mentions the government smear campaign against him without hanging on the point too much. He calmly explains himself in an articulate way, establishing himself as perfectly sane. Then he reaches out to connect and empathize with his interviewer:

> When I hear you just speak, I go "actually this is a thoughtful guy."

When he validates Joe, he validates Joe's audience, and it becomes Snowden's audience. He did this with Trevor Noah too; I think he's intentional about it while very cleverly appearing not to be. It's a good thing Snowden is the one who blew that whistle, and not somebody less calculating.