Early on in the domestication of not only pets, such as cats, but other animals like horses and cows, certain traits were seen as beneficial. Some traits were seen as desirable, rather than purely beneficial. Those traits pleased the owner's eye or sense of proportion, among others. The human had found that by breeding stock selectively, these traits could be achieved. As time went on, such traits were refined.
However, cats and other pet type animals produced the variations at a faster rate, because of shorter gestation periods and higher numbers of births as opposed to large animals. The cats, especially, had a propensity for leaving their master's homes and, even as today, a vast number of feral cats were produced. In the wild, the traits produced by humans were quickly spread and increased among the wild populations. The differing colors, physical size, shape of body and head, etc., are the results of the interbreeding of centuries or millenia...