CA, Serong did a lot of organizing for that bounce, and it seemed obvious who the tap target was, but St Kilda still gave him space.
He helped himself by forcing Brayshaw to go at least 20 meters back of the circle for the bounce. This created space for him to exit back around Darcy, and give the ball to the best possible option, Bolton spreading to space. Both their opponents called it for a bluff and were waiting to pounce on Serong coming out forward of the circle.
Q1, Why did Freo not use this earlier? or did they try?
Q2 Where Saints gassed, not concentrating fully or reacting quick enough? leaving space for the tactic to work so well. Serong had everything covered, space to run into, Darcy protecting Serong's space so no-one could get a hand on Serong, and Bolton's space had him running away from his opponent not into his tackle.