Why are cats so soft? Because there are many joints connected between the bones of cats, the bones of cats will be very soft, so the bones of cats are actually very hard and they are not fragile.
Humans have a long clavicle that connects the shoulders and the sternum, which makes the upper body have a certain width and cannot be folded hard.
The cat's collarbone is small and thin, and the scapula is connected to other parts of the body by muscles. The stretchable and contractible muscles are obviously more flexible than larger and long bones, so they can easily squeeze through narrow gaps.
The spine and limb joints of cats are also particularly flexible, so they can coil the body into an incredible angle of human beings and can twist the body in a short time when falling from high altitudes.
As for the more meat, I believe there are many examples of this in humans. People with small skeletons look much more flesh than people with larger skeletons. The whole body is covered with flesh and small bones, so how can it not be soft to the touch?