I think it was HMR's boyfriend, the happy pictures, S sitting on his lap with her arms around CH's neck, smiling from ear to ear, and the dismissiveness of his and AW's tired warnings of sexual abuse (If it happens, we''ll deal with it, said HMR. WHAT? She wasn't concerned?!). He went out of his mind with anger that in no way could he get her to come home, and, if she married CH, and as she said, if they may move away, she said he would be K's daddy! She stated this publicly on FB. He's thinking, what about S? He couldn't control it any longer. He had zero access to S if HMR decided it was so, and he decided he'd had enough. He had his mother's blessing at that, not to mention her encouragement! There was zero way he could win otherwise. I think they tried to call in CPS but it got thwarted and the new house became a reality. G3 it was mentioned had felt CR1 owed him money from a deal. Did he feel he used that money to buy that house for DR? He supports JW. G4 may have been against the murders, but, in the end, I do think he played a role in planning, purchasing, or was there. As he stated; The Family Has Spoken.
I think Parker put that in there b/c he knows that his client is said to have been there by two different people who were not shown each other's proffers and got enough right to convict him. It's likely a legal tactic to show that he did everything he could to get his client a lesser sentence. He does NOT want to be charged with ineffective counsel.