Why did Leo Tolstoy become a pacifist?

Leo Tolstoy became a pacifist following a profound existential crisis that led him to reject the Russian Orthodox Church and traditional religious institutions, which he viewed as corrupt.1

After studying the Gospels, Tolstoy concluded that the true message of Christianity was centered on the Sermon on the Mount. He distilled this message into five core tenets, one of which was "nonresistance to evil." For Tolstoy, this doctrine did not mean that evil should be accepted, but rather that it could not be fought with evil means, specifically violence.1

Because he believed that governments rely on the threat of violence to enforce their laws, his commitment to nonviolence also led him to adopt anarchist views, enjoining his followers to refuse military service and avoid participation in state institutions.1