"You said it yourself, "The guy revealed government programs that ANYONE who cared to look knew existed decades before.""
I preempted a lot of the Snowden and TAO leaks in my writing on Schneier's blog. I also studied the NSA far back as Puzzle Palace and declassified documents that existed before. The Snowden revelations were not all stuff you'd find studying NSA.
Originally, NSA revelations showed they did what they could to keep Americans out of the collection process. Echelon, for instance, mainly targeted international calls with most of the SIGINT setup outside of the U.S.. Post-9/11, the government's position on NSA and Patriot Act was NSA was getting metadata with FBI targeting individual suspects with NSL's and warrants for "people." Far as foreign spying, Americans figured it was mostly on enemies with allied stuff just keeping fair playing field. Tice leaks showed they were vacuuming up data on all Americans. The Tice and AT&T room leaks indicated they were vacuuming up lots of data which NSA tried to downplay. Drake revealed bad management and oversight at the NSA plus showed what would happen to internal whistleblowers. Binney then told courts and media around 2012 that NSA intercepted all kinds of communications including American emails. That they were collecting everything instead of targeting people.
Now, in 2012, Americans are starting to get the big picture but still claims of 2 or 3 people NSA tried to prosecute as traitors. Then Snowden, claiming inspiration from them, leaks all the specific methods they're using which changes everything. They can no longer deny what they were doing at this point because their own files contradict their lies. That's from domestic all the way through disasters like Belgian networking getting taken down that go way past just keeping tabs. We also find the FISA warrants were targeting criteria applied to whole population's communications instead of warrants for specific accounts or people. Although effective INFOSEC didn't really change, there was a widespread adoption of encryption following the leaks that reduced bulk surveillance a bit plus lots of legal responses that needed information specific to Snowden leaks.
So, there was a huge difference before and after Snowden despite him not being first to tell us they were vacuuming up everything domestic. None of this was obvious for most Americans or easy to prove before Snowden. I guessed most of the attack vectors but even I wasn't sure what they were hitting. It was more "they could do it so we should probably close the hole anyway."