This is especially true if dissenting opinion is filtered before it gets handed to the President etc.
I apologize if the following sounds a little leftist. I only intend to make a point about how mistakes come to be made, and what governments may need to do to arrive at better decisions:
Over in Australia, an ASIO analyst chose to resign rather than see Australia join the Iraq war on the basis of WMD pretexts. (Andrew Wilke is now a Member of Parliament).
The trillion dollar mistake US made was due to influencers being able to feed super-classified information to the willingly gullible people.
It is not easy for a President to call bullshit. I believe the reason is because there isn't sufficient accountability that is built into the system. In days past, members of the royalty are expected to fight in wars. Even during Roman days, only landowners could join the army. The appearance of the professional soldiers lowered the personal risk of the people in power who rush into war.
The Chinese emperors surrounded themselves with eunuchs thinking that the absence of offspring give some assurance that these people will be less biased, but it didn't work out that well. Influence is still peddled, particularly because power itself is very addictive on its own.
Some cultures resort to shamans to try to get an outcome that is independent of any one person's viewpoint. The most interesting one that I came across is the use of ibogaine, where people have a "spiritual" moment, where they see the big picture instead of worrying about themselves.
For a complex society to survive and transcend humanity's limitations, we may need to create a supermind. Some elements of this already exist. One is the idea of "opensource intelligence" that can be used to corroborate otherwise secret accounts.