Sorry, my bad.
I've never personally seen a judge reject a plea of guilty to the originally charged crimes, but I've seen a judge reject a plea deal for reduced crimes (lesser included charges). But yes, a judge SHOULD be aware of the underlying facts and circumstances of the crimes/charges; I'd be of the opinion that most judges only have a cursory understanding in most minor cases; certainly federal judges will be acutely aware in major cases like Manafort).
Most jurisdictions allow a judge to have discretion to reject a plea deal agreed to by the prosecution and defense, but I believe there's a minority of jurisdictions that require a judge to accept an agreed plea (federal judges are not so required).
Also, in most jurisdictions, a judge can accept the plea but not accept the agreed upon sentence. Usually, the judge retains the sole discretion (absent any statutory reqs) to sentence in any way he/she chooses.
