Snowden himself is not particularly popular these days. If there isn't an outright majority who view him as a traitor, then it's certainly a sizeable minority. Opinions were almost evenly split back in 2013, and opinions on pardoning vs. prosecution were likewise evenly split when this was polled in 2017 (about 30% each, however). And over the past couple of years, the intelligence community appears to have convinced many more people that Snowden is a Russian asset - I suspect American attitudes towards him have cooled somewhat, or perhaps become partisan.
If you look at polling on concerns about surveillance in general in 2015, it was pretty much an even split, with a slight majority who were concerned about surveillance.[0] A majority did say it was unacceptable to surveil American citizens, at 57%, with 40% saying it was acceptable - I would not call that a vast majority, though.
Even if somebody says they're against this sort of mass surveillance, that does not change anything unless people vote based on it. Like it or not, things like surveillance and war take a back seat to all the other issues voters care about, especially since those two are among the least likely to actually affect the individual voters in question. The result of this is that few Democrats are going to vote for Rand Paul or Ted Cruz just because they happen to position themselves against the NSA or war in Syria, and few Republicans are going to vote for Bernie Sanders based on the same, even if they have strong preferences against surveillance and war - and that's ignoring the fact that there are definitely people on the other side of these issues, who believe that pardoning Snowden and withdrawing from Afghanistan is bowing down to Russia or something.
Ultimately, people get the government they deserve.
[0]: https://www.pewresearch.org/internet/2015/03/16/americans-pr...