Suzzie, one of the things I did as part of my own healing was to read a book that was written by a psychologist who worked with sex offenders. It gave me so much insight into why sex offenders do what they do, and the most powerful healing came from understanding that a huge part of why sex offenders do what they do is because they have little or no empathy for others, and because they are selfish. That's all. They have an urge and they don't care about what impact their behavior will have on others. They do care about possible consequences to themselves, however, and will usually intimidate, threaten or otherwise terrify their victims into silence.
So basically it is most likely that your father and his friend did this to you because of THEIR need for sex / power/ domination or whatever. That they did it to *you* is likely simply because you were a child they had access to.
It was never about you, or anything you did or said or wanted or didn't want. Some men - unfortunately all too many, my own father and his friends incuded - are like that and will 'use' (abuse) any child/ren available to them to satisfy their own needs, without any regard whatsoever for the well being of the children.
It was ALWAYS about them. ALWAYS because of them. Always.