Echelon[1] and Room 641A[2] (and others) were well known among niche circles a long time before Snowden. These "conspiracies" were the kind of thing that people would call you a crackpot for if you told normies though.
A reason others may refer to conspiracy theory supporters as "crackpots" could be attributed to the fact that there's now so many wild theories out there (UFOs, aliens, 9/11 inside job, etc). So if you support a few, then you'd be more likely to be considered a crackpot.
In other words, while those two examples were true, many are likely not.
[1]https://en.wikipedia.org/wiki/ECHELON
[2]https://en.wikipedia.org/wiki/Room_641A