It seems like they moved the article to tkrunning.com, which is a Medium custom domain created before Medium custom domains were disallowed. From there, tkrunni

It seems like they moved the article to tkrunning.com, which is a Medium custom domain created before Medium custom domains were disallowed. From there, tkrunning.com is behind CloudFlare, so I would guess they used CloudFlare's Page Rules, which lets you (among other things) setup 301 redirects at the CloudFlare reverse-proxy level.