Snowden, and Greenwald by extension, are perfect examples of how being right about one thing doesn’t make someone right about everything. I also have serious problems with how Snowden chose to whistleblow, though the actual whistleblowing was necessary.
There were a lot of options for non-extradition before Russia. Even the route he took when he fled doesn’t make a ton of sense unless he’s selling the information to America’s security competitors. My guess is he genuinely believed in leaking the information and he got paid to do it by one or more foreign countries.