The development of steam technology is a great metaphor. The basic understanding of steam as a thing that could yield some kind of mechanical force almost certainly predated even the Romans. That said, it was the synthesis of other technologies with these basic concepts that started yielding really interesting results.

Put another way, the advent of industrialized steam power wasn't so much about steam per se, but rather the intersection of a number of factors (steam itself obviously being an important one). This intersection became a lot more likely as the pace of innovation in general began accelerating with the Enlightenment and the ease with which this information could be collected and synthesized.

I suspect that the LLM itself may also prove to be less significant than the density of innovation and information of the world it's developed in. It's not a certainty that there's a killer app on the scale of mechanized steam, but the odds of such significant inventions arguably increase as the basics of modern AI become basic knowledge for more and more people.