Well, the unexpected twists play a major role. In many of these short ghost stories, things don't go as expected. For instance, in 'The Monkey's Paw', the family thought the wishes would bring them good, but instead brought tragedy. The idea of something from the beyond interfering with our normal lives is also scary. In 'The Red Room', the presence that the man encounters in the room that was supposed to be just a superstition is a terrifying concept. And the use of vivid descriptions, like in 'The Tell - Tale Heart' with the description of the old man's eye, makes the horror more palpable.
In many of these stories, the element of the unknown is really frightening. For example, in 'The Bell Witch', the family never knew exactly what the witch would do next. It could be a sudden noise or a physical attack out of nowhere. Another scary element is the feeling of being watched. In 'The Amityville Horror', the family constantly felt as if unseen eyes were on them. And apparitions, like the 'Brown Lady of Raynham Hall', are terrifying because they seem so real yet are not of this world.
Scariest short ghost stories are scary because they tap into our primal fears. We are afraid of death and the afterlife, and ghosts represent the unknown side of that. Also, the settings in these stories, like dark and lonely places such as old houses, cemeteries, or deserted roads, add to the fear factor. The brevity of the stories also leaves a lot to the imagination, which can be scarier than detailed descriptions.
The unknown factor. In the scariest true ghost stories, there are often things that can't be easily explained. For example, in the story of the Enfield Poltergeist, objects moved on their own. No one could figure out how or why. It's this lack of understanding that sends shivers down our spines.
The unknown element makes them scary. For example, in the case of Old Changi Hospital, no one really knows what exactly happened during the war there. All we have are rumors and the feeling that something horrible might have occurred, and the spirits of those who suffered are still there. It's the mystery that sends shivers down your spine.
The element of the unknown makes them scary. In many of these stories like the Dyatlov Pass incident, we don't really know what happened. There are no clear explanations for the deaths of those hikers. Also, the presence of the supernatural. In the Amityville Horror story, the apparitions and strange noises seem to suggest a supernatural force at work, which is a very common and scary element.
The unexpected appearance of the ghost is often the scariest. Like in a story where you think everything is normal, and suddenly a ghostly figure pops up out of nowhere. It gives you that sudden jolt of fear.
The sense of the unknown is really scary. In these short stories, like when you don't know who the ghost is or what it wants. For example, in the story of the figure in the mirror, you don't know if it's a malevolent spirit or just a lost soul.