The key thing about ideas that are "brilliant and obvious in hindsight" is that the world was already ready for them, and so nothing needed to change for them to happen; i.e., they don't have any prerequisites that aren't already in place. They "just" needed someone to actually notice that there were some pieces that could be fit together in a novel way.
There's no word I know of that captures this idea of "the world being ready for" the idea, though. Is the idea "incremental" in hindsight? "Elegant" in hindsight? "Free" in hindsight?
Photolithography, for example, is intuitive, and far simpler as a technique for constructing circuit boards than what came before it; but etching circuits using light projected onto light-activated chemicals isn't one of these "the world was ready for it, someone just needed to do it" ideas. Someone thought of it, then needed to do a whole lot of work to get it to happen, finding the right chemicals, experimenting with projection technologies, etc. After the fact, the idea of photolithography is extremely intuitive; but it wasn't a better-term-for-"obvious in retrospect" idea.
Neat, I learned a new word.