Why is whole milk easier to foam?

Milk fat exists in a small crystal ball coated with a thin film of protein and fat, and the film of each crystal ball can prevent the crystal balls from colliding with each other and form a larger fat bubble. In addition, the film protects the crystal ball from being digested by enzymes, making the milk less sweet or not sweet at all. In the process of heating, the protein in the milk increases and makes the milk thicker, so whole milk foams better, and more fat means more protein film, which produces more lasting foam, do you understand?