Both of these were true, but not terribly significant except as interesting anecdotes. (And Captain Crunch did go on to become something of a legend himself which makes him historically significant.)
No, I'd say the number of folks able to do that sort of thing back then was about as great as it is today. Back then, there were a lot of electronics hobbyists out there... people who built their own home stereo gear, people who built ham radio gear and used it. Lots of folks got extensive electronics training in the military during the war and that lead to a big hobby electronics boom in the fifties and sixties.
Sure, they could well have been blue-boxing. They also could have been going into telephone cabinets and stealing a pair that was in use, effectively using someone else's line to make their calls. That was also a very popular college student trick back then.
--scott