Why does a dog eat it’s young?
Because the dog is hungry.
Many animals eat their young if they can, particularly males. Sharks eat their young.
Animals do not have morals or ethics. They are motivated only by survival instincts.
Humans are not much better. They kill each other all the time. What can we expect from lesser animals?
When this puppy grows up he'll kill those cats or some neighbor's dog if not the neighbor or owner themselves.
Humans anthropomorphise animal behavior. In truth the cat or dog "loves" you because you feed it.