Because he identified the potential risk of superhuman AI 20 years before almost everyone else. Sure, science fiction also identified that risk (as people here seem eager to point out), but he identified it as an actual real-world risk and has been trying to take real-world action on it for 20 years. No matter what else you think about him or the specifics of his ideas, for me that counts for something.
As far as I can tell, all he did was open a forum for people to write fanfic about these earlier ideas.
https://web.archive.org/web/20100304171507/http://lesswrong....
Plenty of people have been beating that drum for years.
Your original made no mention of sci-fi, and made it sound as if no one had imagined a malicious AI before yudkowski
(edit: you can see that https://news.ycombinator.com/item?id=38116456 responds to the scifi part of my comment as well and was posted before yours https://news.ycombinator.com/item?id=38116494 (if my assumption that ids are chronological is correct))
If you want AI gone wrong, Magician's Apprentice.
If you want misalignment between what you wanted and what you actually asked for, Greek myths, Midas or Tithonus would both suffice.
"${my favorite work of fiction} mentioned/alluded to it too!" does not make that work of fiction equivalent to a serious take on the topic in real-world context.
It originally credited Mr. Yudkowsky with being the first person to imagine ai as a serious threat to humans, without mentioning that the trope existed in sci-fi, or mentioning sci-fi at all
The pre-edit text must've sounded funny, as from what I remember of Yudkowsky's writings, he frequently referenced old sci-fi tropes about or related to AI, commenting on their relevance and applicability in the real world.
The whole concept is farcical.
As for real world risk… well, an AI with some kind of personality disorder might not be much of a realistic risk today, but even assuming it never is, there are still plenty of GOFAI that have gone wrong, either killing people directly when their bugs caused them to give patients lethal radiation doses, or nearly triggering WW3 because they weren't programmed to recognise the moon wasn't a Soviet bomber group, or causing economic catastrophes because the investors all reacted to the phrase "won the Nobel prize for economics" as a thought-terminating cliché, or categorising humans as gorillas if they had too much melanin[0], or promoted messages encouraging genocide to groups vulnerable to such messages thanks to a lack of oversight and a language barrier between platform owners and the messages in question.
[0] Asimov's three laws was a plot device, and most of the works famously show how they can go wrong. Genuine question as I've not read them all: did that kind of failure mode ever come up in his fiction?
It would be nice if the world worked that way. Then we could diminish any risk just by writing a lot of scifi about it :)