While he did a laudable thing, Snowden ain't Nelson Mandela.
Nelson Mandela wasn't 'Nelson Mandela' when he was sentenced to life in prison either.
See Nkonto N Sizwe, the Church Street bombing, Winnie Mandela's spree of "necklacing" (burning people alive with tires around their necks), etc. Mandela is not a saint nor a great leader.