I think Medium's high domain authority makes it easier for articles to rank higher on Google. Not saying that article aren't good. I think from medium's perspective, they make money only from paid users, so it's in their best interest to promote content that serves paid users. Although medium does pay you if an external user becomes a paid member. I've had many days with only external views, but still being paid a small amount.... probably bcoz the user became a paid member later.