The horror genre is packed with geniuses. If your story's gonna take place in space, there has to be a couple of astronaut brain-boxes. If there is a destructive AI or murderous computer, there's bound to be an egghead with three PhDs who knows how to defeat it. If the story centres around a virus that caused human civilisation to collapse, there's guaranteed to be at least one bonafide mad scientist.
In the real world, scientists and government officials would have protocols to maintain their safety. But in movie world, so-called geniuses have to act dumb for the story to plunge into horror. In a scary movie, a physicist that rivals Stephen Hawking will make an error of judgment which no rational person would make. A master inventor will ignore a design flaw that anyone with common sense would notice.
Although it's annoying when "smart" characters make stupid decisions, sometimes it's the only way for the story to work. After all, if Frankenstein thought resurrecting a corpse may be a bad idea, there would be no movie.
But even when you take this into account, you can't believe a supposed genius could act as dumb as the people on this list.
10. Astronauts Takes No Precautions With A Super-Advanced Alien - Life
In Life, a group of astronauts on the International Space Station find a probe returning from Mars, only to learn it's carrying a cellular lifeform, which they call Calvin. Calvin rapidly evolves into a a complex organism, showcasing his ability to turn into a muscle, neuron, or photosensor cell in an instant. Because this sort of mutation is unprecedented on Earth, the scientists cannot be too careful while handling Cal.
Instead, the exobiologist, Derry, starts experimenting on Calvin immediately after his team captures him. Unsurprisingly, Derry is completely unprepared to handle this hyper-evolved specimen, and finds himself being attacked by Calvin.
Instead of keeping the alien quarantined in Derry's lab, the engineer, Rory, opens the door and attempts to kill Calvin with a flamethrower. This gives Calvin the opportunity to kill Rory and escape from the room.
Even though it was incredibly stupid for Rory to enter, it was non-sensical for him to use a flammable weapon while surrounded by combustible machinery and chemicals... in space. The fact that he didn't blow the whole station up with the flamethrower is a miracle.