Victor Frankenstein wanted to play God. He wanted to be the first man to create a perfect human being that would be free of disease. Victor thought little of anything else besides his own obsessions. He failed to think forward as to what his creation would look or be like. He used various body parts from criminals. Some of them were pulled from the grave. He thought only of the success element and never as to how he himself would react to the "man" once he awoke or what needs the man would have. Victor's own vanity was his fatale mistake.
His mistake was not in creating the monster, but rather in abandoning it. Victor decides to play God, and indeed, for all intents and purposes, he IS God. But instead of teaching the Monster what is right and wrong, morally acceptable and unacceptable, he abandons the creature. Really, is the monster so very unlike other human beings? He seeks companionship and experiences an intense need for revenge when he is wronged. So what does all this say about religion?