[Loquebantur]

This is a common misconception. The US system of state secrets for example is enormous, and while leaks do occur, they are negligible compared to what is kept hidden.

There are multiple tricks employable, one is to keep any single collaborator in the dark aboout most of the conspiracy. That way, any single leak is manageable.

Your conviction of believing conspiracies to be unrealistic is common and helps conspirators a lot. It disincentivises whistleblowers in particular.

[lern_too_spel]

> The US system of state secrets for example is enormous, and while leaks do occur, they are negligible compared to what is kept hidden.

Not from those whose job it is to find them. The Manhattan Project leaked to the Soviets multiple times over. Any time the government does something illegal, a whistleblower has leaked it to reporters.