Did you not read this bit...
An international panel of medical experts has provided case summaries on all 17 babies who featured in the 10-month trial of Lucy Letby.
The 14-strong panel concluded that no criminal offences had been committed at the Countess of Chester Hospital in 2015 and 2016 and instead provided alternative causes of death.....
...and the list which follows it, which essentially says that none of the babies were murdered.
The thrust here is not that they failed to stop Letby. It's that she was not culpable - they were. The negligence was towards the babies.
Now, I don't have the qualifications to make a definitive judgement on this. And I suspect that practically no one here does either.