Personally, I'm pretty happy he did such a crappy job with the murder if it was going to happy regardless. That said, I've long held the theory that AM had help from CE in the actual murder and that his "attempted suicide" was in reality a botched attempted murder of CE so he could pin the crime on him. Maybe Eddie got the drop on AM and maybe he held some piece of damming evidence as leverage.
Think about it, suppose Paul's phone is never cracked or the video never recorded or AM gets rid of the phone. Suppose further that AM kills Eddie and pins the murders on him at the same time. I still think the financial crimes come out and AM is sunk, but he might have seen that as a way out.
BTW, I got some inside dirt last night. This is from inside the Taj Mahal. Alex would send an intern across the street to the Murdaugh family bank with an $80k check. He would bring back cash and give it to AM. He would be in a closed-door meeting for an hour or more with Flemming, the bank president, and the sheriff. Maybe AM coincidentally wanted cash for some other purpose, or maybe those were payoffs.