This is my guess as well. Perhaps, since
Pennsylvania is a state that still has the death penalty, he has agreed to a plea bargain in order to take that off the table.
I'd been hoping, considering LE's relative silence, that they had known from fairly early on exactly what sort of situation they were dealing with and that it was just a matter of processing evidence and getting all their proverbial ducks in a row, and now it seems clear that probably was the case. It does make me wonder what they found -- evidence of a hastily-cleaned crime scene? bloodstains in a vehicle? a weapon?
Even from the little they have released, the circumstances have pointed in a singular direction from the beginning, and the more certain people pushed the narrative that she had voluntarily left, the more suspicion they directed at themselves. Could they really have believed that everyone (Beth's daughter included) would have bought the narrative that she'd just taken a bunch of cash and disappeared?
It makes me think that her death was due to a sudden, impulsive act of violence, rather than something that was planned out ahead of time.