When OpenAI was founded, the mission was to develop AI, but nobody (anywhere) knew how to do AI, so OpenAI did ML research on games instead, which is what DeepMind was doing (with Google's perceived AI/ML dominance being the raison d'etre for OpenAI, and Google having just bought DeepMind). This was the era when Karpathy was at OpenAI.

Around the time Karpathy left, Ilya Sutskever, another OpenAI founder, started playing with Google's new "Transformer" architecture, which was the beginning of the "GPT" series, GPT-1, GPT-2 and eventually ChatGPT (GPT 3.5 + RLHF). In retrospect OpenAI's early Transformer experiments and GPT-1 was the inflection point that moved OpenAI from a company that wanted to build AI, as soon as anyone else did, to one that was actually doing so, although I think it would be revisionist for anyone to claim they knew what they were doing at the time. The early GPT-1 and GPT-2 papers read more like "wow, this is a bit unexpected, look at all of the things it can do!".

Karpathy left OpenAI in 2017 for Tesla, came back from Tesla in 2023 and left again in 2024.

So pretty sure the original poster is talking about 2017.

GPT-1 presumably, which was released a year after he left. Prior to focusing on GPT, OpenAI was pursuing a lot of research directions.

Well Karpathy left in 2017, and all the sort of commercial stuff didn't happen till a while later - for example they set up the structure to take external money in 2019 and that's obviously the point at which they'd found the pathway that justified doing massive training runs and all that. So Karpathy was out very early (left at the point that Musk thought OpenAI had basically failed).

The inflection is Right before its meteoric rise.