But what is important is that Egwene believes it. On the old site, I posted a semi-joking theory as Dark Cannoli (mayheRIP) that Mesaana had become infected with the Aes Sedai mindset which distorted her priorities and perspective, which led to her ignoring the summons to the Cleansing in favor of concentrating on her schemes regarding the Tower. What if that is what happened here? Egwene had so bought into the myth of her superiority and the greatness of the Amyrlin Seat and meanwhile, Mesaana has become so caught up in the affairs of the Tower that it gives her just the merest second of doubt which is enough to cripple her in the face of Egwene's willfully stupid perspective combined with Two Rivers stubborn adherence to it.

The issue here is not so much that Egwene undersells the legends of the Forsaken, but that she overestimates the Tower and the meaning of her occupation of the office of Amyrlin Seat. Other people beat the Forsaken through badassery, Egwene does so because she's so stupid that she overestimates her own importance and cannot see how ridiculous her thesis is.