"Ev Williams (founder of Medium, Twitter, and Blogger) is well-connected in the tech and startup communities due to his past companies, so he was probably able

"Ev Williams (founder of Medium, Twitter, and Blogger) is well-connected in the tech and startup communities due to his past companies, so he was probably able to easily convince a lot of famous tech/startup people to switch." Good point, also don't underestimate Medium is a progression of Twitter. Simple sign-in with ready made Twit handle recognition.