What exactly is Substack? I asked a few weeks ago if it was the new Medium, and that was apparently the wrong way to ask the question because it got downvoted through the floor.
I think medium catered to bloggers, and gave a space to post easily, and get some extra viewership through their community.
Substack caters to more prominent writers/bloggers who want to charge for their content, and build a following, and handles the logistics of that.
So maybe something like Patreon and Medium combined
And like Medium, one day Substack too will be filled with inane musings from nobodies and hustle/entreporn content.
The difference is that instead of being designed as a blog with a strong domain ranking and an RSS feed, it's a web page with a strong domain ranking and an email signup interstitial.
One thing he noted was his number of readers went up too though (probably due to appearance on #1 nationwide talk show, that promotes the IDW/Dark Enlightenment Movement/"race realism"/ancient aliens Egypt hypothesis, just before he moved though).