I am not the author of the site in question, but I suspect that your guess is right, and that Pandoc is the hub between the spokes.
For my blog, I write posts in Markdown. Then the build process uses Pandoc to convert the posts into web pages and, for certain pages, PDF files typeset with TeX. For example, here is a post in both web and PDF versions:
(Web) https://blog.moertel.com/posts/2024-08-23-sampling-with-sql....
(Typeset PDF) https://blog.moertel.com/images/public_html/blog/pix-2024060...
Beautiful. I don't suppose you have public, detailed installation steps for how to go from "nothing exists" to "Pandoc can push posts to https://blog.moertel.com/"? :)
The best I was able to do was http://github.com/shawwn/wiki, which has been broken since 2020. You can't spell Haskell without Hell.
If you wouldn't mind pulling up a `claude` in your repo and running `/init` and showing the result, that'd give me at least a vague idea of what to do.