Well, when you look at the events surrounding the 'Poltergeist' movies, there were a number of rather strange and tragic occurrences. There were deaths and accidents among the cast. The media loves a good story, and they latched onto these events. They started to connect the dots and create this narrative of a curse. As the stories spread and more people talked about it, it became a significant part of the True Hollywood Story. It's a combination of real - life tragedies, media attention, and the public's fascination with the idea of a Hollywood curse.
It probably originated from the rich folklore and mythology about jinn in Islamic culture. The idea of a curse might be added to make it more of a horror concept.
Sukuna does die in the manga. The way it happens is quite dramatic and ties in with many other elements of the story, adding depth and tension to the overall narrative.