I am really disappointed in the family for this comment. I was ragged on for believing that the family had a need to believe it was all ET's fault, and here is the proof. It suggests they are trying to shift blame to ET by ignoring TH's culpability. They have not addressed their evil son/brother at all.
Arthur would also be alive if many things hadn't happened, namely lockdown. But With TH's lack of empathy and love for his son, there would have always been the latent risk that he would do something terrible to Arthur. The gun was already loaded, in the form of Thomas Hughes' lack of parental love and responsibility, lack of capability as a father, inadequacy as a man, resulting false pride, and man-child tendencies. It only took the stress of being forced into full-time fatherhood, combined with a relationship with a woman who hated his son, in order to pull the trigger.
I will believe for now and for evermore that TH was the worse abuser, up until the day before he died.