These dichotomies trouble me greatly and to me, make no sense.
Mentally deranged enough to kill 2 people with extreme violence VS controlled enough to keep quiet about it for 7 years
Out of control murders VS careful concealment of remains
Crazed killing VS long-running, well planned financial fraud
These don't align at all.
Yet we know the facts to the right are correct.
So we have to question the facts on the left.
I think we are looking at a group, not an individual; planned executions not rage; prosaic motive, not emotionally complex motive.
I don't know any more than anyone else here about Holdom, but if the reports of his personality are true and he is really just an overgrown child, while he may well be involved, I can't see him being either the main protagonist of the murders or the person who has covered them up and mislead/misdirected people for 7 years.
Of course, it is always possible he is a criminal mastermind who has cunningly hidden behind the facade of a simpleton for 40 years, but I doubt it based on what we know of his lifestyle.
With the utmost respect Jane, but ...
"controlled enough to keep quiet about it for 7 years". You have more chance of a sole operator, or a couple who have history keeping it quiet than a group. The more people involved, the more they talk, the more gets leaked. I don't think there was that much "control" involved, in any case.
"careful concealment of remains". They weren't that carefully concealed in my opinion. Karlie's body was found in about 18 months from when she was murdered. And it's quite possible that Khandalyce was just kept because whoever killed her couldn't think what to do with her remains, or they were quite secure where they were. When they were found in the suitcase, everything started to unravel quite quickly. Nothing careful about it in my view.
"well planned financial fraud". I wouldn't say it was well planned at all. If it was well planned, they wouldn't have left a trace. The audacity of fronting up to Centrelink, the Credit Union, all the transactions, quite frankly, it was only a matter of time before they would be found out.
You may be right - it could be a group, but I personally lean towards a single person with the possible involvement of a partner, ex partner or friend who had history with the offender (for the fraud), and the same again with the possibility of a family member who helped cover it up (I only say that because of the birth certificate of Khandalyce's that was found by police. I'm not saying she was specifically involved, but may have had knowledge after the event). On the evidence so far, I can't see the way clear to think in terms of highly organised crime groups. But I've been wrong before ...
7 years isn't really that great for getting away with murder. In fact, it's not much time at all.