No, you are not reading too much into it. Many have spoken about how Mr. step-and-fetchit isolated Anna from family and friends. Appears that was his mission in life.
That's the first thing a sociopath will do to his/her victim. Isolate them, and sometimes incapacitate their target (I hate the word 'victim'), by drugs or other means.
This is exactly what Howard did. He smelled a huge pay off in the form of J. Howard Marshall's estate. No way was he going to let that slip through his fingers. Unfortunately for HKS (and Daniel, Anna, and Dannielynn)he went too far, like sociopaths usually end up doing.
I hope and pray that he and KE don't manage to wiggle out of their crimes.