Why doesn't the hunters killing affect the future in the sound of thunder?

In "A Sound of Thunder" by Ray Bradbury, the hunters' killing does not affect the future because of the careful, controlled nature of time travel. The time travel company ensures that no significant changes occur in the past, allowing only predetermined events to unfold. However, the butterfly that is inadvertently killed by one of the hunters symbolizes how even small actions can lead to drastic consequences, ultimately resulting in a drastically altered future. The story emphasizes the interconnectedness of actions across time, illustrating that seemingly minor events can have profound impacts.