It looks like the child's physical custody was returned to the mother but the state still had legal custody of the child.
Whether or not CPS officials could be criminally liable for what happened to Maleah depends on the facts. Some were charged out here in CA in the abuse death of Gabriel Fernandez:
An 8-Year-Old Was Brutally Abused for Months. Why Did No One Save Him?
What I see here, from your link, is that Maleah was living with grandma, mother and mom's boyfriend when she went to the hospital on July 10, 2019, due to throwing up blood and lethargy.
Next, she was taken to the hospital on July 28, 2019 for a cut on her forehead. Still living with the same people.
Finally, still living with mom, boyfriend, and grandma, she was taken to the hospital in August, 2019, for a horrible head injury and bleeding in her brain.
Suspected child abuse was reported. CPS took the kids away. But ultimately could not confirm the abuse and allowed the kids to return to mom's physical custody in February of this year, while retaining legal custody, monitoring the situation and mandating parenting classes for mom and boyfriend. Neither have taken the classes yet.
Now, two months after Maleah was returned to mom, she's missing and I think we all know she's dead.
It's not hard to figure out, IMO, that this poor child was the victim of systemic abuse.