Well, it could be the unique atmosphere it creates. In the 'best jumpscare amnesia custom story', the setting is often dark and mysterious. The unknown elements lurking in the shadows add to the sense of dread. Plus, the sound effects play a huge role. The eerie noises that build up tension before a jumpscare are really effective in making it terrifying.
One idea could be exploring the backstory of the mansion itself. Maybe it was once a normal house before the spooky events started. Another could be focusing on a particular character's experience inside the mansion, like how they deal with the constant jumpscares. And a third idea might be to create a story where the characters find a way to break the curse of the mansion.
A brave and curious journalist could be a main character. They are always looking for a big story and think the mansion is their ticket to fame. Another could be a paranormal investigator who has been studying spooky places for years. And a young, adventurous kid who got lost and ended up at the mansion by accident.
Definitely not a true story. FNAF is a work of fiction that takes place in a fictional world with its own set of rules and scenarios. It's all about creating a thrilling and immersive gaming and storytelling experience, not reflecting reality.