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Maybe it all comes down to the fact that some EN girls didn't know what they were getting into, really. Both from a "joining a JP company" point of view but also "doing idol work and all of what that entails in the background".
This is why girls like Kiara, IRyS and FUWAMOCO do well with it because they understand what's going on and how things work.
But the likes of Ame, Gura or Fauna would be susceptible to clashing with it due to not really understanding what it all entails beforehand and maybe it proves to be too much or too inconvenient.