They know they're lying. We know they're lying. They know we know they're lying. Yet they hold us in such contempt they expect us to believe their lies.
Well when two plane's hit two buildings (designed to survive airplane impacts of this kind) and three buildings fall down and people swallow that nonsense then they may well hold the public intellect in low regard.
Ah, but only a few really swallowed that tripe. Most people question events, even if only in private.