Pretty sure they quit as an act of public activism about some popular political issue. Unfortunately, when scientist are also activists, they can no longer be objective. You don't see mass resignations when other crap papers get published. If it doesn't embarrass them politically, they accept it.
I think it's a combination. Bad papers that reach conclusions scientists agree with will be generally ignored, while bad papers which reach conclusions they don't like will trigger protest. This is especially problematic in fields where individual studies are extremely noisy and meta-analysis is needed to see the truth. Because the meta-analysis then just ends up showing the prevailing bias.
