Nothing is rogue when you point your DNS to someone else's host. Because you pointed a domain you owned at GitHub, it was then possible for GitHub to obtain a certificate for your domain. Sure, maybe something was missed in the terms of use, but this is something everyone needs to understand. Pointing your domain at someone else's server allows them to get a certificate for that domain. That's how domain validated (DV) certs work, it's how they've always worked.