People certainly knew about the NSA “Echelon” program long before 9/11, 2001, too. I remember distinctly discussing the fact that the Government monitored all phone transmissions as early as the 1980s with some of my friends. The fact that it was popularly and officially denied didn’t mean that it was any surprise. Perhaps this is one of the reasons Trump’s “conspiracy theories” are so popular — they are partly true. Personally, I’ve been making references to such events (Roswell, the JFK assassination, etc.) for a long time, waiting for people to start taking Reality seriously.
As far as Oliver Stone goes, he is a master film-maker and I’m sure anything he creates is worthy of study, but I think historical accuracy isn’t his intention, or he would probably have focused more on the unjustifiable release of details of other programs than the eavesdropping and metadata gathering.
The other problem I have with Snowden is that he stole 1 million documents, but didn’t bother to save any evidence whatsoever (not a shred!) that he ever tried to report suspected malfeasance through appropriate channels. How can you explain that?