They never had control or they never lost it?
edit:
On the subject of trying to keep powerful and/or dangerous knowledge locked away from the general public, one of my older HN comments[1] was about the larger, long-term problem our species' rapid access to new knowledge and powerful technology.
We need to figure out how to safely integrate new technologies into society asap.
[1] https://en.wikipedia.org/wiki/Lysenkoism : "More than 3,000 mainstream biologists were sent to prison or fired or executed as a part of this campaign instigated by Lysenko to suppress his scientific opponents."
[2] https://en.wikipedia.org/wiki/Suppressed_research_in_the_Sov... : "Law of large numbers or the idea of random deviation were decreed as "false theories". Statistical journals and university departments were closed; world-renowned statisticians like Andrey Kolmogorov or Eugen Slutsky abandoned statistical research."
This is pretty damn close though: https://en.wikipedia.org/wiki/Illegal_prime
That distinction is important - physical things like people or papers or computers can be controlled and hidden. It's much harder to keep knowledge itself bottled up, because there is always a risk that someone clever will discover it on their own.