Of course the Moetzes is for the klal, and in their roles as Moetzes members, this is their focus. As roshei yeshiva, their focus needs to be on the yeshiva, and as rebbeim, on their talmidim. They often have roles as husbands and fathers as well. Sometimes there can be a conflict of interest between their various roles, and they have to do their best to figure out what the ratzon H’ is.
So you are going back to my original argument, that since there is a conflict between what is good for the Klal and for the individuals, they have decided that individual Limmud HaTorah (and therefore maintaining the imbalance of available boys to girls) is more important in the eyes of Hashem?
To quote myself:
As I have said in the past, the Roshei Yeshiva (specifically BMG) are very happy to have an imbalance between boys and girls; it allows boys to stay in learning longer, and allows them to stay in Bais Medrash instead of needing to be able to support a family before dating.