You yank them up and down. Cats see them as feline enemies and things to neutralize. Swinging cords by an open window with a breeze are a threat.
Many cats read Marine Corps tactics about setting up an ambush from two fronts. Here we see Shiloh who has just leaped at a venetian blind cord and popped it up high. Her brother Trouble snagged it with a paw swat and has brought it in for the kill:
In this photo we see Shiloh ready to leap at the cord while her brother lays in behind a speaker to lend close support:
And in this photo we see two cats coming at me to steer me away from recording their "cord kill":