Let’s look at the footwork. We can’t go looking at it blindly though. Swing on the left is an offspeed inside pitch where he gets his foot down early and waits back. This is a great move where his weight and hips stay back and he literally rotates and turns on this pitch. That’s why you see the elbow triangle stay through the whole swing. He can’t extend here. But notice the back foot rotates to allow the back hip to turn out of the way which allows the upper body to turn through the ball. Also notice the front foot. Weight is on the heel and that has to open up because of all the rotational force from the backside. You can’t keep that front foot planted and closed while allowing the hips to open. If the foot stays closed then you slide and don’t rotate.
In the swing on the right, that’s a fastball middle away and down. He gets to extend here. But the footwork is similar. It’s not exact because on the left (or top) he has to completely turn to get inside. On the right (bottom) he has more freedom to drive the ball and stay in the ball. Body still rotates just not as violent and sudden. Front foot doesn’t need to turn so much because force is going more towards center field than the left field pole.
Point here is that when you see a swing, keep in mind that it’s pitch dependent. The swing and body has to adjust to pitches. Your core mechanics are key but every swing is different. It has to be. Don’t look at a swing and emulate it blindly. Look at a swing and know when that swing is happening. Take some key things ad apply it to your swing. Your personal swing is all about timing and confidence. Do you… Do what makes you feel like you can win that at bat. Of course there are a hundred other things to consider but here we are talking footwork and energy direction and ability to adapt.