I don't see a blur.
I need to see more evidence.
If you look at the soldier in between the one in front and the tall black soldier, you'll see his head is moving and it too is blurred - albeit slightly.
Look close it's been photoshopped out... look like a "water stain" streak running down the photo where the cord would be
There's a faint shadow of a blur right up the front of the girl onstage.
look to the left of her hand, you can see the color of the background is darker along the wall.. that's where the chord moved bottom part of the chord did not move while the shutter was open, but the top from where it "disappeared" up to the top of the photo it did.. hence the blur effect.
Look to the right of the door in the back - you can see a shaded area that runs all the way up - that is undoubtedly the cord that was in motion when the shutter clicked.