Here's why:
* Focus on realism: Naturalism emphasized portraying life as it truly is, including the harsh realities of poverty, violence, and social injustice. Crane's works like "Maggie: A Girl of the Streets" and "The Red Badge of Courage" depict the struggles of individuals in these environments.
* Determinism: Naturalism believed that human behavior was largely determined by heredity and environment. This is evident in Crane's exploration of characters caught in circumstances beyond their control, such as the soldiers in "The Red Badge of Courage" and the impoverished characters in "Maggie."
* Social commentary: Naturalist writers sought to expose the injustices of society and the plight of the underprivileged. Crane's works often criticize the social systems and inequalities that contributed to the hardships faced by his characters.
While Crane's writing also exhibits elements of realism and a focus on psychological detail, his strong emphasis on the determinism of environment and his social commentary align most closely with the Naturalist movement.