Scientists had understanding of nuclear fission and how nuclear physics work. It was theoretically possible before it became practically feasible.
We have no idea what intelligence really is ("resilient, distributed system" is not universally accepted as definition, even more to really mean something outside of analytic definitions if such have any use at all, to say the least), how it works, how a theoretical system could function as "generally intelligent" in concrete terms. Intelligence as we know it is a property of living organisms. It is a phenomenon. What "artificial intelligence" may even mean and if it is possible to create "intelligence" artificially is mere speculation. We face real existential threats that are not mere speculation, as we do not even know whether the ways we affect the planet may lead to a habitable environment for humans or not.