They wrote there that they were looking at Elixir because they did not like the direction Python had taken. I'm sure Python can do the same as JS but Elixir is just so much nicer. Which is also my experience.
Your point obviously stands, pretty much all of mentioned can do the job.
Seriously i will not choose JS today if i have.a very specific requirements for choosing Elixir or Python (or any other stacks here).
In reality, people choose the stack they're get used to. But it's their limited ability to see JS strength to solve their issue in first place. It's not informed choice.
At the very end of the day, I think some people just don't like JavaScript.
At the risk of speaking for people other than myself, a lot of people don't want to write code in JS and if they don't have to, they won't. Frameworks/tools like Phoenix and HTMX or the fact that many languages can compile to javascript/wasm mirrors this opinion