I also think it is possible that a person beyond DW could be involved in this case, but not necessarily onboard with the murders. A person could have felt coerced, or just desperate for cash and didn't think through the possible consequences and so just went along with a terrible plan that went awry. About five years ago, I worked with a very nice, quiet, well-liked church-going, talented, hard-working family man in an ad agency.
On Valentine's day night, he called to say he was coming home to make cookies with his kids. But he never made it home. His pregnant wife was distraught. Our whole company and LE went looking for him night and day. His car was found. He was suspected to be dead. Turns out, he staged his own disappearance, drained his and his wife's bank about, ditched his young children and pregnant wife, changed his name and moved to LA. He had been leading a double life, swinging with couples at seedy sex clubs and was, in fact, a complete fake. (I'm not sure if I am allowed to post his name here. But it was INSANE. No one, not even his closest family members or a single one our our coworkers EVER would have suspected him to be capable of that. There's a documentary about it.
He presented himself on social media and everywhere else as a sweet family man. He was the opposite.