If UFO’s have existed before the 1900s, why did UFOs only start being a scary thing around the time of Roswell and the atomic bomb?

Someone please educate me on this if I’m wrong but you have lots of stories talking about UFOs and alien beings being evil or that they’re not our friends but it only seems to start around the time of Roswell.

Before that time, no one is reporting scary experiences (that I’m aware of), only mysterious craft and lights in the sky, there’s even positive events like the Hopi people being guided by a star in the sky (most likely a UFO) and being saved by the ant people through two cataclysms. Did we humans cause this change to happen and this is what significantly changed the trajectory of things around Roswell or have UFOs always been potentially a threat and I’m just missing something?

You have people with UFO sightings saying the beings were beautiful people and their experiences were amazing and then you have another group saying they’re evil but my point is, this idea of UFOs being potentially evil only seems to start around the time of Roswell and after the atomic bomb.