Sweeping ban waves seems to be their M.O. when they want a certain kind of people gone. They don’t want you to be able to regroup right away elsewhere on their site. I remember a large number of subs getting removed because of one post on /r/alright (wasn’t even bad). Looked like something similar happened earlier this week with /r/milliondollarextreme and related subs being banned all at once as well.