I think because one day everyone woke up and heard about PRISM, including a lot of the tech companies, which had to go into damage control to deny their involvement. It was big news with brands that every American was familiar with.
That explains why Snowden was a big deal, but as soon as we all figured out that PRISM wasn't what he claimed it was (and Greenwald stupidly believed without running the docs he was given by experts) and instead just a data integration project for processing communications from targeted foreigners, Snowden should have become a smaller deal.
