It seems to me like the biggest things are impossible to see with a "normal" outlook. It's as if you either can't see the big thing, or you see it in a fantasy world, a fiction of some kind (science or otherwise).
Take connecting the entire world. Even after the technology existed and had been deployed (the very early system that gave rise to the internet as we know it), people didn't look at that early version connecting a handful of places and think, "Wow, this could connect EVERYONE!" They didn't stand there, looking at the terminals of two connected computers, and imagine a connected world like the one we live in today. They didn't talk about ecommerce and social media global events being reported on in near real time. No one had to roll their eyes, because no one was making these grand claims.
I can't find the link now, but I read somewhere that it took YEARS after the Wright brothers had achieved first flight to get the attention of the world. People didn't see how transformative that thing could become, yet the proof of concept was there.
When you look at all the big tech moments in (recent-ish) history, the car, modern computation, the PC, aviation, you don't see people coming out with these grand declarations before the fact. And it's not for lack of intelligent, visionary people.
So it makes me wonder, whenever a person makes such grandiose plans, and they're not fiction writers, what's so different about them that they'd be able to see so far ahead?
Maybe they're different. How would I know? But history makes me skeptical.