Here's a wikipedia page on the topic, since it's much too deep a topic to really understand here.
The ad-hominem stuff seems inappropriate here, Gates, Hawking, Musk have identified this as a credible threat, so saying "grow up" isn't really a sufficient argument. Also arguing only 90% of humanity would die isn't really much consolation.
[1] https://en.wikipedia.org/wiki/Existential_risk_from_artifici...
Nothing here plausibly describes a mechanism that is a true "existential risk" - the risk to the existence of humanity.
My argument stands and I don't defer to Gates and Musk and even Hawking - high level hand wavey statements without any plausible description of the mechanism just don't hold up. Famous names should not be automatically assumed to be right - certainly not with Elon Musk.