To illustrate the point that conspiracy theories seem convincing because they are untestable and nobody cares to test about it, I am proud to announce

The Isolated Building Conspiracy Theory

This "isolated building CT" is a theory that states (for my location) that the world is only the places I have visited up to now. All of the news from other places are invented by the authorities. The world only contains the places where I have traveled to. Trains to an imaginary place called "Mongolia" end up in government prisons where all passengers are killed and replaced with flash clones teleported to the Beijing railroad station when "their journey has ended." All Internet sites from outside the building are actually operated in the building through purposefully congested lines. And the whole thing is floating in the middle of nowhere.

See, nobody can disprove this to me. I just sit tight on my chair in my house, and anybody who claims to have traveled elsewhere automatically becomes part of the huge cover-up. My theory can stand against any person! Just don't actually get me on a plane to Africa, and Africa doesn't exist!!!!!

This is how most conspiracy theories work. They rely on ignorance. 9/11 CTs rely on the fact that you don't know about building physics and crash physics. If you happen to pick up a NIST report or even a textbook on demolition and plane crashes, you'll get the flag of "undercover government spy." For the Moon Landing CTs, the theorists rely on ignorance of photography and astronomy.

In fact, I can claim that every single law of physics is made-up and is wrong. As long as I don't actually learn physics, any physicist or college student is simply part of the conspiracy.