NJ is smart enough to realize that MHJ is a devil herself, but she's a devil who they are comfortable with and can trust at a certain level. Meanwhile everyone else at HYBE sees NJ as enemies they want to get rid off, SourceMusic, BELIFT, Pledis, BSH, they all have their own groups and favorites, and that doesn't include NJ. They will get bullied and sabotaged because it is in the interest of those pro-HYBE entities for NJ to fail so their groups can take more of the market share.
True even though MHJ is shady,she's never harmed newjeans, she's always pushing the members to pursue more and more opportunities. So I see why the members would still support her.