Numerous things. Maybe they are trying to get someone else. I really don't understand how LE works. Look at Skylar Neese in West Virginia. Two of her friends stabbed her in the early morning hours of July 5. They were the last two she was know to be with. They took her to the woods and stabbed her, left her body there. This was premeditated.
One of the girls broke down and confessed on Jan. 1. She was being harassed by classmates on Twitter. Took LE to her body shortly thereafter. They couldn't confirm (or didn't release) that it was Skylar's remains until the first of March. Two months.
Although girl #1 confessed, she didn't have to turn herself in until May 1 because they didn't have enough on girl #2 until then. That day or maybe the next they arrested girl #2. So LE knew from Jan 1 who did it, why and they had a body, but it took until the first of May to make the arrests.