I bet you we are all wrong and some random person is going to vibe code himself into something none of us expected. I half kid, if none of you have see it, highly suggest https://karpathy.ai/zero-to-hero.html
It seems to be more nuanced than what people have assumed. The best I can summarize it as is that he was doing rather non-standard things that confused the LLMs which have been trained on vast amounts of very standard code and hence kept defaulting to those assumptions.
Maybe a rough analogy is that he was trying to "code golf" this repo while LLMs kept trying to write "enterprise" code because that is overwhelmingly what they have been trained on.