Why does JavaScript not have a dominant CMS/blogging platform?

Ghost was probably a great contender, just didn't rise to the same popularity. I still run my blog on it. WordPress really rode off the high of Control Panel, which was based on and included PHP and MySql, therefore required almost nothing more than putting files in a directory on your $5 a month shared host.

WordPress at first didn't even require any special PHP extensions (if I'm remembering that correctly) which would have needed to be turned on by the server admin, nor did it require shell access which was almost never available.

WordPress built itself on the most available, cheapest, platform at a time when blogging was rising and peaking in popularity. These conditions aren't there anymore, so anything else just doesn't have the potential market.

What are you really asking here? Why is there no Wordpress but instead of PHP, you'd use node? If you're wondering why there's no "Flask or Django for node" I would say there most certainly is.