Then they started adding various annoyances, which I'm sure they thought would help with financial goals, but it eliminated the "simple, attractive" part. As a reader, seeing that a link went to medium.com used to mean it was easy-to-read and text-focused, and afterwards, it meant that it would be full of intrusive crap one would have to deal with before reading. To the point that people started making [special browser extensions](https://chrome.google.com/webstore/detail/make-medium-readab...) just to remove them.
As a writer, whose main interest is in people reading my stuff (rather than, say, monetization), I wanted to move it somewhere where the readers would not be annoyed and maybe refuse to click on the link in the first place because of the domain.
I'm sure the above describes many others' experiences as well.