The plane where the film rests in a 35mm camera tilts when the whole camera tilts (see the dotted line on the camera). The camera has to tilt to include the whole building in the frame, but top of the building is farther away from the film plane. The resulting distortion makes the building appear to be falling backward in the finished picture.

35mm Camera
View Camera
View Camera with corrective tilt.

  I got it!