Here’s a great visual for how the force and the center of mass line up in an ideal scenario. A golf club does not change weight when you swing it, but because you are applying force to that golf club, effectively it does change weight. The golf club will act as a pendulum if you let it.
If you take this to the top of the swing, and you allow this weight to swing in line with where the handle is, it’s going to swing pretty effectively and if you let the head get too far behind you, the force you need to apply is significantly higher. It’s also not going to swing around you very quickly. That’s where better players struggle.
The poor golfer gets the club working too much in front of the handle, meaning there is no natural squaring or natural swinging to that. The more you can control the mass of the club around your body, the more effectively you can swing and square your club for best impact.