If you really want to know why and how ChatGPT works, here is a fitting post about it: Stephen Wolfram explains the basic mechanisms, how the probabilities are calculated, how neural networks work and how ChatGPT uses all that concretely.
It’s a long post and you need some pauses to think about it. But I think it’s worth reading.
https://writings.stephenwolfram.com/2023/02/what-is-chatgpt-doing-and-why-does-it-work/