I think it's probably straightforward: Medium is very focused on providing a venue that is attractive to them whereas the others you mentioned are not nearly as

I think it's probably straightforward: Medium is very focused on providing a venue that is attractive to them whereas the others you mentioned are not nearly as focused. And the team behind Medium is top notch. Having a founding role in Blogger, Twitter & Medium probably makes Even one of the great entrepreneurs of our time, certainly in media/publishing.