They underestimate the likelihood of black swan because it is very hard for adults to concretely imagine things that have not happened before and then even temporarily fully believe ~"dreams will come true."

One of my go-tos on this is the Fukushima nuclear accident. IIUC there were plenty of folks in Japan who knew of the high risk. Perhaps many interested in nuclear energy outside of Japan, too.

But the average adult if asked about the prospect of a major nuclear incident occurring say, "tomorrow," would narrow their eyes in skepticism. There's almost an instinctual level seeding of doubt.

This can be a good thing. LK-99 was an excellent test of the dissonance from dramatic changes in reality and costs of inaccuracy.

The greatest VCs I have known are exceptional at suspending disbelief to test their ability to basically shape world building.