Yes, IMO, there are two profiles LE may be working with:
1. A delusional stalker of SG's took the life of NG to get SG's attention they deeply crave, as opined by OPs here. By taking NG's body that disposing it in the desert or mountains, NG's anguish is in their control. They prolong that as long as possible for pleasure. The ransom escapades get them NG's direct attention.
2. Perp(s) who invaded NG's home as theives, unexpectedly end up with a deceased 84 year old woman. If she was on anti-coagulents or blood thinners as her bruised and bandaged arm suggest, NG could have bled out internally from injuries sustained during a struggle (i.e. aspirated blood on the front porch). In their warped, small, sociopathic mind(s) they took NG's body to dispose of it in the desert or mountains. And then they got the idea to ask for ransom for an easy cash (or bitcoin) windfall. But with no proof of life, there is no payout.
Just my morning speculation. IMO.