Chatgpt is just Cortana with better marketing. AI isn't smart, it's just algorithms producing a facsimile of language via pattern heatmaps. What was Cortana if not just an earlier version of the same thing?

Well no, not really IMO. Cortana as far as I know wasn't based on LLMs as we know them today, it was a way older method of NLP. You're right that on a high level it's pretty similar but the underlying technology is qualitatively different IMO.