There really was a breakthrough in chatbots. Happens all the time in science.
People get a really great new idea, all the smart people jump on it, the field is burned out in six months.
This revolution in science
https://en.wikipedia.org/wiki/Renormalization_group
didn't last long enough to finish grad school.
That idea of "build a language model by predicting the next token" was floating around for a while, I was in two startups that were trying similar things long before it was really feasible.
First we were trying to make something that could write fake abstracts for clinical reports from PubMed as a proxy for clinical notes with LSTM, GRUs and such.
Later we were training CNNs to complete a battery of classification tasks and believed this could make a "foundation model" that could be trained to new tasks easily.
I had a long list of serious problems that doomed many lines of development related to what I was doing and when BERT came it was clear to me that subword tokens were essential (e.g. word vectors are doomed because half the time the most important word isn't in the dictionary!) and also that attention addressed the problem nobody really wanted to face with LSTM which is that in a story about a person you have to copy that person's name and variations over and over again.
It wasn't clear to me that transformers were going to be as successful as they were.
It helps also that there was a big investment in training technology. Often technological revolutions happen when there is a surplus in the base technologies. For instance, experts in 1970 anticipated we were going to get something like the WWW in 1980 but it was really 15 years late because there was no single company that was going to make the end-to-end investment to bring it to the mass market, excerpt in France
https://en.wikipedia.org/wiki/Minitel
(The TRS-80 Color Computer wasn't really intended to be a computer to teach kids BASIC, it was intended to be a terminal for teleagriculture!)
When the web came out, however, the cost of investment in making it work had dropped so low that it didn't take one company to invest in an optimized end-to-end system, rather a bunch of little investments (like the one people made in a 32-bit PC) added up to a network that looked like the computer on the bridge of the Enterprise.