Just speculating about something that leads me to believe that AM already had it in mind to eliminate Maggie as a means to protect their money and property from the wrongful death suit. A fail safe if the situation became necessary. It's the paper found with Maggie's will that had her sister's name crossed out and Murdaugh Sr.'s name written in that I'm thinking about. If AM wrote this intending for Murdaugh Sr. to put the proceeds of the will into an untouchable trust upon Maggie's death, it would keep the estate intact. Upon her death, it could have been signed and dated and notarized with a date previous to her death. I am not saying there any notaries that would put their seal on such a document nor am I saying AM's father would be a party to this. I don't know how hard it would be to forge a notary seal and I don't know if in South Carolina a change like that would require notarization.
The sudden illness and hospitalization of Murdough Sr on the 7th was a shock and I don't believe AM expected him to pass. IMO he thought he would recover and be able to probate the will. He hadn't thought far enough ahead to create a fail safe for his fail safe.
IMO it was the visit with the CFO that day that tripped the fail safe switch.
MOO, JMO