Young's stance is a little wider than most players. That stable base lets him make an aggresive shift towards the target on the downswing, without fear of falling over.

Pay attention to the width of Cam's swing arc. While amateurs tend to have a narrow arc and take the club back mostly with their arms, Cam stays very wide by moving his arms and torso together.

Again you'll notice the width in his arms here, but note how his upper body remains centered over his lower body. In the past, Cam's tendency to sway away from the target here led to inconsistencies in his ball-striking.

A backswing benchmark for Cam is making sure his left knee drops towards the ground. That feel helps him explode off the ground in his downswing.

Cam used to come over the top. Now he gets the lower body working toward the target while he pins his arms, club and upper body back. It makes it look like he’s standing still, but there's no conscious effort to pause.

Look at how Cam's left knee has moved outside his left foot. A key sign of a big side-to-side shift.

Remember that wide arc? Here's why it's so important: It gives the clubhead more time to pick up speed by the time it gets back to impact.

Notice how his left foot is nearly off the ground here. Dropping his left knee towards the ground on the backswing helped him push back off it in the downswing.

For amateurs I'd recommend practicing your swing in slow motion. If you can land in a balanced follow-through position, you'll be able to do it when you turn up the speed like Cam does.