I always took the theory of betrayal trauma to be that the very people who are supposed to protect us are either our abusers, or fail to protect us from our abusers, because they chose to ignore the abuse, or believe the abuser, or support the abuser by refusing to act.
Both of my parents betrayed me, as well as several other relatives, one was the abuser and the others who stood by and refused to act while I was violently attacked even as a toddler, in front of their eyes. As a result of my families betrayal, a lack of trust in anyone became ingrained, I grew up taking responsibility for the abuse because no-one stopped it from happening, and all of their behaviour reinforced the belief.
I grew up not only believing I was to blame, but that I was defective and unacceptable and wrong in every way, because we are taught that we have to love our parents no matter what we feel, it leads to denial, and minimization because we need to rely on these people for our very survival.
For me the affects of being betrayed had as much of an effect as the abuse, because it lead to lasting changes in my self perception. I think it lead to my self hatred, an inability to trust, an inability to accept love because I believe I am undeserving, and beliefs that I was defective and made them act that way, it was lasting, it didn't cease when the abuse stopped.
I continue to work on the beliefs that were instilled as a result of the betrayal, they are very lasting and have become automatic. When you have an audience to the abuse, and your a child, and no-one acts, you believe it must be you that is making it happen.