When you can’t find an existing solution to do something “simple” like convert an exported Google Chrome bookmarks HTML to JSON, it helps to be a programmer so you can build your own.
Check out my public GitHub code repository at: https://github.com/jsnelders/chrome-bookmarks-converter
I also have it running live at: https://chrome-bookmarks-converter.netlify.com/
It’s quick and dirty and only took a couple of hours but it work.