Of course, part of it is that people are more likely to vote 3rd party when they know who the 3rd party candidates are, and this year Johnson and Stein got a lot more media attention than they did in 2012, and were even included as options in almost every major poll from about ~May or so onwards.
As for *why* the 3rd party candidates got more coverage this time....sure, it's because people didn't like the major party candidates very much. But I actually think it's more on Trump than it is on Clinton. The Republicans who were looking to find an alternative to the major party choices were heavily overrepresented among political/media elites, which lies in stark contrast to the Dems dissatisfied with Clinton. There were plenty of current and former Republican members of Congress, for example, who refused to vote for Trump, who then publicly deliberated about who they might vote for instead. This resulted in the media paying more attention to who the alternative choices might be. Whereas the #NeverClinton Dems were just ordinary voters, not political elites.
So I actually wonder, if the GOP had nominated a more "normal" Republican like Rubio, then would Johnson and Stein have actually gotten that much coverage? Would pollsters have included them as options in polls?
Yes, it's true that the fact that the third parties got more coverage is more on Trump than Clinton, but when election day actually came around third parties took more votes from typical dem constituencies than they did from typical rep constituencies. Disappointed republicans came home far more in the final weeks than disappointed democrats did. I will also note that while most of the #NEVERTRUMP politicians stuck to their guns and refused to vote Trump to the end, they were mostly writing in random names or voting for Clinton - not voting for actual third party candidates. Politicians like Rigell (who voted Johnson) were the exception among NeverTrumpers, not the rule.
