You can only say such things with hindsight. In the moment, nobody knows what the future will hold. Take the space program in the US for instance. In 1969 we landed a man on the Moon. We'd repeat that several times until 1972. At that point Nixon made a speech which implied various unpleasant things about space's future, but he'd be out of office, disgraced, a couple of years later, so how big a deal could it have been anyhow?

I think almost nobody from that era would have believed you if you told them that more than 50 years later not a single human would have traveled beyond low Earth orbit, and that we'd now be struggling to recreate what we did in 1969. Furthermore a significant chunk of the world doesn't even believe we landed on the Moon anymore, no doubt in part because of this apparent anachronism.

It's not like there was any sort of collective or even singular decision to just let things die out. I mean sure Nixon did his thing intentionally, but even as a President in the golden years of the US, he was still just one man.