I suspect the following:
1. Kidnapping for ransom gone wrong.
2. Victim dead due to violence or natural causes due to stress of the kidnapping, heart attack perhaps.
3. Buried in the desert somewhere.
Agree-simple motive-fancy neighborhood full of rich people that any 2 or more amateur criminals would find attractive, especially if they were observant and working nearby-they don’t have to be with the cartels-or intelligent.
Watch a few houses to see who appears to live alone, pick a time not many people are around, disguise yourself, get yourself and your partner into the house one way or another. Grab and restrain the occupant, try to get her bank info, etc first thing.
I think that is where it went south, if someone was hitting/choking the woman for bank info, etc-they accidentally killed her. So they carried her body out, went into the desert and buried her, then maybe tried to get ransom anyway from the relatives-no cartel, no conspiracy, etc, etc-just a theft/kidnapping that turned into murder. Seems obvious...
I heard a blood spatter expert say that she did not walk out. Because the spatters were continuous, without gaps that would be caused by her feet is she were walking, he determined that she was carried out. I can’t recall if he said she was wrapped in something.