Knowing what happened. As for the people getting off the plane in Ohio, US... I do see people discredit the whole idea of the "conspiracy theories" because of a few crack-pot theories they heard.
I think a wiser person would realize the significance isn't that we know exactly what happened, but that there is enough evidence to see that the official story has huge holes in it, and is likely impossible.
The significance is that we have been lied to, and additionally that some other forces are at play.
There are some suspicious ties to Moussad, Israeli intelligence, as this video describes.