The transformer architecture on which (I think) all recent LLMs are based dates from 2017. That's only "multiple decades after" if you count x0.6 as "multiple".
Neural networks are a lot older than that, of course, but to me "these things are made out of neural networks, and neural networks have been around for ages" feels like "these things are made out of steel, and steel has been around for ages".
Except this isn't new. This is after throwing massive amounts of resources at it multiple decades after arrival.