In the upper part of the swing, the golf club remains at a fixed angle to his arms (since his wrists are cocked). But in the lower part of the swing, the golf club begins to "go loose" and the angle between it and his arms begins to increase rapidly (since his wrists are now uncapped), and the club then shifts dramatically toward the outside. At the bottom of the swing, the golf club is almost perfectly parallel to his arms. This is where contact with the ball is made. Part of the physics of a golf swing (from the golfer's perspective) is finding the release point (wrist release) so that at the bottom position, where the player's hands are directly above of the ball, the golf club is in the low position. the vertical position parallel to his arms. This will maximize club head speed at impact and result in the furthest distance.