Easy advice to give as a bystander lacking context (2013!), hard to follow as a "martyr" living in that context. It wasn't even clear whether he'd be a martyr (he could have easily turned the politics around, wouldn't be the first time in the American history).
I was definitely around in 2013. And it was quite clear at the time there will be government persecution for the leaks, I mean that's why he ran in the first place.
If you stand on the path of martyrdom for your people you should be prepared to follow it to conclusion rather than fleeing to the sworn enemy.
Well the sworn frenemy has a crude but fitting idiom for that I suspect you might be familiar with, and Snowden might be too now: пиздеть - не мешки ворочать.
I have huge respect for people that have passed the test of going against their environment and comrades to do what they think is right (even if/when I disagree with it or it harms my interests). You can argue that he was insincere or a double agent (this is definitely wrong), you can argue he's a traitor by endangering people who had nothing to do with it (weak argument IMO), but arguing from an armchair that he must have walked full length is just silly I think. Let's have an extreme and inverted thought experiment to test your views. Imagine someone blows the whistle about FSB's Ryazan sugar [1] today, must he not run and let his head be smashed with a sledgehammer in a prime time TV show?