I'm nearly 60 now (where did the time go???) and I have been extraordinarily blessed in family and friends. Thank you.
I too don't think it's fair to blame the parent(s). They don't always see what's going on when they're not around. Like Grainne Dhu said, it's usually NOT a stranger but someone trusted. The child's attitude or actions afterwards may not always be detected by someone who can recognize there's a problem.
That IS what makes it so difficult to detect these pervs. It's quite often someone you already have trust in to do the right thing. IMHO, these are the ones that do the most damage and have the larger number of victims because they are so hard to be detected.
They are often quite charming, ooze sincerity and reliability. They're often patient and establish a level of trust before doing anything wrong.
And... I don't know how to put this because it sounds horrifying. I don't want to offend anyone, so if anyone reading this is easily upset, maybe it's time to stop reading here.
Often, if the pedophile is patient, the child is flattered and "in love" in the beginning. I know in my case, it was such a relief to have a grown up to talk to about all the awful things my mother was going through, who paid attention just to me at a time when I wasn't getting as much attention as usual at home. I knew, even at the time, that my mother was terribly ill and that my dad was coping as best he could with working and trying to do all the stuff my stay at home mom did (this was back when most mothers stayed at home!). But that didn't stop my feelings of loneliness and all the fear I felt. So the concentrated adult attention felt good, felt flattering and I was happier for awhile.
At first, a lot of pedophiles just push the boundaries a tiny bit--a hand strays a quarter of an inch too low or lingers a tenth of a second too long. It feels uncomfortable but it's over so fast that the kid wonders if anything really happened. And then the pedophile piles on more attention and possibly gifts, outings, special favours, etc. If the child doesn't like it, they feel uncomfortable because they feel obligated because they are accepting so much good stuff (attention, gifts, etc).
So it's not like one day the child is fine and the next day the child is distraught and freaked out. It can start out very slowly and build over quite a long period of time.
From what I've read, the man who molested and eventually raped me actually moved relatively quickly; I think it's because he knew he had such a hold over an unusually vulnerable kid.
If the child objects, the perpetrator pretends their feelings are hurt, tells the child that they misunderstood or (eventually) tells the child that it is the child forcing the perpetrator to do those things. Another ploy that predators use is to keep asking the kid if everything is okay, so that the child imagines they are giving their own consent to what is happening.
Even when the molestation gets very bad, there's often a lot of good stuff for the child mixed in, so that the child has seriously mixed feelings about the perpetrator. Which adds to the child's sense of guilt--they feel like they love the perpetrator and they feel disloyal for even thinking they don't like something the perpetrator does to them.
It is rape, there is no doubt in my mind. But it's a rape where the victim was often cajoled into participating, which does a terrible number on their minds. It can take a victim many, many years to realise that they really were the victim of rape, that they weren't capable of giving consent.
I don't know if I'm explaining this right. The sense of conflict and discomfort in the child often doesn't start right away, so that when the child starts showing behavioural differences, the pedophile is already an established part of the child's life and is less likely to be seen as the cause of any changes in the child.