That was based on the original reports of when and why Venus returned to Michigan. It was supposedly because she had discovered that he was abusing one of the children and she filed a report once she returned. Apparently the prosecutor declined to press charges because of insufficient evidence. When she filed that report LE would have done an investigation, which would have included interviews and such with the children. Any evidence used in the current trial presumably would have come from those interviews. If there was enough evidence to press actual criminal charges they would have done so since that is a serious charge, but presumably either the nature of the accusation was marginal or accounts they got from the children were too vague. In a civil case the standard of proof is lower, so it is possible to make a finding when there is still significant doubt. A civil finding is inherently less serious than a criminal finding for that reason, it is not the same thing. The difference is "it did happen" versus "it might have happened".
The child protection services agent who appeared before the judge would have stated that the claim was substantiated, meaning that in his/her opinion there was some evidence to support the claim, and that allowed the civil case to go forward. However, presumably the evidence was not strong enough to support a criminal charge.
