RSBM
My personal theory is that the CPS visit led to the women discovering what Devonte had been up to with the neighbors. Unlike the earlier incident with Hannah, which was panicked, this was a deliberate act of rebellion. I think, once CPS left, there was some intense interrogation going on in that house, and either Devonte owned up to what he’d done, or one of the other kids cracked.
I think the frantic departure of the whole family was more Sarah and Jen’s last ditch effort to enter the “honeymoon” phase of the abuse cycle, and get the kids back into line, rather than an attempt to flee CPS. They’d dealt with CPS before, and they probably thought they could fool them again. But it was crucial that the kids be onboard with that.
But… I don’t think it worked this time. I think by the end of the weekend, it was clear that the kids (at least some of them) weren’t going to be cowed, and that the whole fantasy world they’d constructed and carefully protected was about to come crashing down. IMO, that’s what ultimately lead them to drive over the edge of that cliff.