Why? Not everyone is resume grifting. It is fast, solid and has excellent developer workflows. Lot of stable (oh no, no updates for 10 years because it just works!) libraries. With CLOG it is a nice secret weapon with people wondering how you managed to move that fast. At least in our experience but we make products so we don't have to explain what it is made of or why.
This is almost like a satire. But I've found it rather funny. It presents question and provides an answer which is contradictory at first but still makes sense.
In their defense I can understand going into this article expecting it to be "why I chose Common Lisp [over other programming languages]", rather than "why I chose Common Lisp [over other Lisp dialects]" -- I think most of the HN audience are not people who are often using a Lisp dialect, so their question going in would be "why not use the programming languages I'm more familiar with?"
Meanwhile, "why I chose Arch Linux" is more likely to be interpreted as "...over other types of Linux" because most HN people are already familiar with the decision of "which Linux distro will I use?" But if you gave that headline to someone who doesn't have much familiarity with Linux they'd probably expect the article to address why they chose it over Windows or Mac.
(I don't think "why I chose Common Lisp over other Lisp dialects" is an absurd premise for an article like the person you're replying to does, but I can at least kinda see where they're coming from)