Why aren't there any absurdly popular anime girls under the age of 12 besides NanoFateYate and CCS? Chiyo doesn't count, she's more of a mascot character. 14 seems to be the cutoff, when people are able to start taking them seriously.
You really don't want girls under the age of 12 to make important decisions like fighting supervillains in a crowded city or how to fix the universe
Nipah's like...a zillion years old
Here's a hint OP, what's 4chan's name in Japanese?
She acts her physical age when she wants to, with the added bonus of having the immaturity of a real little girl. She's the perfect example of why 2D is better.
>Why aren't there any absurdly popular anime girls under the age of 12
You seem to be forgetting Maruko-chan who is likely more popular than any of those mentioned in OP.