>>106565746
That's probably because it was always part of the original Nogizaka concept to be more refined and 'higher class' than other over the top idol group concepts.
And it actually worked in the sense that they managed to draw a pretty significant amount of female supporters as well, which was pretty rare at the time. At one point I think it was 2:1 m to f, which was pretty good considering female idol groups are primarily targeted at men, and actually impressive that they managed to expand the market by changing the style and approach.
Especially when comparing to say AKB or or something which was basically the opposite, concept of 'every day idols you can meet, regular girls etc'(and they had a much more skewed ratio of male fans).