The short story “The Black Cat” focuses on several themes which at times are seen interacting and intersecting with each other. The theme of happy family life changing towards violence and theme of freedom and confinement are prevailing in the story. Drinking excess of alcohol became a reason for the unnamed narrator to witness a change in his nature. He was a jolly person living with his wife and his pets who were very dear to him. Later, he grew violent and harsh towards them which ended in killing them. Though he wanted to hide everything, his fate turned everything upside down, resulting in his imprisonment. While writing these incidents from prison he declares himself saintly than he was before. The time when he was free and lived with his family he turned to be harsh and a murder but when his life got confined behind the bars of the prison, he became calm and even confessed his wrongdoings.
i think it's because his owner don't want him anymore because he is weak now, and he can't get back to his owner unless he becomes stronger than a lion.