I thought Einstein or that other guy, Eisenhower or whatever, created the nuclear bomb, before them there was no way of killing so many people at once and the nuclear holocaust was impossible, countries thought they could exterminate the other side and survive, but because of one of these two people the sudden realization and idea that we could annhilate everyone on Earth was created, that no country would survive the aftermath and civilization would disappear.
Was it just like the same way we can predict and hypothesize about AI taking over even though we're not even close to a dangerous AI yet?
Einstein played only a minor role in the creation of the atomic bomb. I assume you mean Oppenheimer as "the other guy" (who played a major role).
Anyway, to your general question, yes, things like science fiction, intersecting with areas of scientific possibility, meant that people thought about nuclear weapons and even nuclear warfare long before the atomic bomb was actually a scientific fact. The chemist Frederick Soddy wrote a popular book about the possibilities of atomic energy (The Interpretation of Radium, 1908) which inspired the science fiction writer H.G. Wells to write about the possibility of atomic bombs (The World Set Free, 1914), which set off a multi-decade period of speculation about somehow unlocking atomic energy and possibly destroying the world. By the 1920s you could read about the possibility of "angry atoms" destroying the planet in regular newspapers.
The scientist who enrolled Einstein in his minor role in the bomb project (writing a letter early on), Leo Szilard, was explicitly a fan of H.G. Wells and cited science fiction as one of the things that "primed" him to see take the possibility of atomic bombs seriously. So he was among the first who, after the scientific phenomena of nuclear fission was discovered, immediately saw how it could be applied to the possibilities of weapons.
The thing to keep in mind is that H.G. Wells' ideas about what atomic bombs were, and what their implications were, did shape how people of his time — including world leaders, like Churchill and Roosevelt — thought about the possibilities. But the actual realities ended up being quite different from what he anticipated. The actual atomic bombs didn't work or act like the ones he dreamed up in 1917, and the world didn't turn out the way he thought it would as a result (he thought that it would lead to a sort of world government policed by a bomber corps). So while this kind of "anticipatory" thinking certainly does play a role in history, we should keep in mind that history often has its own thoughts on the matter!