Hugo site, deployed to public/ directory in html, gives weird results

I have a Hugo site with lots of folders and subfolders, containing both _index.md files and many others. It uses the docsy theme.

Running hugo server displays the site correctly in the browser at localhost:1313

When I run hugo or hugo -D to get the same pages as HTML files on the disk, and I get

• a set of folders...
• ... containing only index.html and index.xml files,
• but no other files. All the other files are missing.
• links look like the raw .md file (example: [VPAT](https://docs.axway.com/bundle/AccessibilityVPATS_allOS_en_HTML5/page/Content/accessibility.htm)
• The index.html files are unstyled, unlike the pages generated by the hugo server command.
• I don't see how to use the index.xml files.

Here is an example of the files and folders produced by the hugo command:

public/
   index.html
   index.xml
   docs/
      index.html
      index.xml
      admin_intro/
         index.html
         index.xml
      troubleshooting/
         index.html
         index.xml
...
      

Here is what the .md file structure looks like

content/
   en/
      _index.html
      search.md
      docs/
         _index.md
         admin_intro/
            _index.md
            amdin_page_1.md
            amdin_page_2.md
            amdin_page_3.md
         troubleshooting/
            _index.md
            ts_page_1.md
            ts_page_2.md
            ts_page_3.md
...