The great mystery of Haachama. Tokino Sora has a similar intimidating reputation but that one can be explained, Haachama on the other hand not really. She must have built quite a reputation before her descent, but it's hard to grasp how. She was never as famous as Fubuki or Miko, and not as experienced as Sora or Suisei. In terms of singing, dancing or any of the other "idol" things, she is definitely good, but not head and shoulders above the others like that reputation would imply.
My best guess is that she's either a completely different person IRL, or it's something intangible that I can't grasp. Maybe she somehow appeals to women?