Why did Victor Frankenstein not try to be nicer to his monster?

Because he believed the monster was cruel and inhuman. All of the monster's actions only brought sadness to Victor, so he didn't try to be kind to the creature.

Explanation:

The monster created by scientist Victor Frankenstein is the result of the yearning for knowledge of the mysteries of life's production, just like Faust, whose ambition for wisdom and immortality made him sell his soul and lose the true love of his life. Prometheus's theft of sacred fire, the covetousness of the forbidden fruit, and the fall of Adam and Eve, which cost them the loss of paradise, show their ties to the fantastic romantic work. What seemed like the progress of the human spirit, the pinnacle of the endeavor to which Victor had devoted all his energy, began the avalanche of misfortunes that forever sealed his fate. All the woes of the scientist's life were caused by the monster and for this reason Victor does not try to be nice to him.

Because he believed the monster was cruel and inhuman. All of the monster's actions only brought sadness to Victor, so he didn't try to be kind to the creature.