“then why aren’t they arrested and charged.. .”
I imagine with over 400 of them they need some time to do some discovery before they start charging. Some are victims, some may be perps, and I’m guessing a lot of the adult women are both.
Also they probably have many witnesses to query, for instance, the lost boys who have been kicked out.
DNA test results need to come back.
It is a huge number of people and I think you need to be realistic about the amount of time the investigation will take. Also, how could they do an investigation while letting all those women and kids live there? The abuse would continue, the alibis would be reinforced, and the uncooperative could get hurt or disappear.
416 are "children", that might include some of the mothers of younger children.
They'd better start charging pretty soon. You've heard of Habeas Corpus, I'm sure, it's in the Constitution. Without evidence, and formal charges, they can not be held for long.