I think that "by necessity" is not true here. A smaller organization can not do as much as a larger organization. Ok, a handful of people could stage a coup. Then what? They still need bodies for tax collecting, law enforcement, jailers for the secret prisons, whatever. Those people need information to do their jobs, which increases the circle size, etc, and we're back where we started.
Assange's insight into clandestine organizations as information networks that can be disrupted is profound. You get the choice between large, effective, and open; or small, ineffective, and clandestine.