In the famous movie, Dorothy is in the magical land of Oz and wants to get back to Kansas. She approaches what she thinks is the Wizard, a giant projected image with an amplified voice. Her little dog Toto accidentally pulls down a curtain and we all see that the wizard is an ordinary man with a microphone and a projection device.
In a very famous line, the man has the projected "Wizard" says, loudly:
"Pay no attention to the man behind the curtain!"
The phrase has become a saying or image for the relationship between a false, larger-than-life, powerful image and the weak "man behind the curtain" pretending to be something he is not.