Generally this would be quite plausible except for the fact that the 1960s and 1970s was a rebellious and openly anti-authoritarian period in both US and European history. That serious abuse of this kind and extent would go completely unreported, not even to any of the parents or any of the friends and neighbors or to any civil authority of any type is highly problematical and at least intuitively impels a suspension of belief.
I was thnking more of the earlier decades when I mentioned the chaos of Germany after WWII. But I don’t think the non reportage in later years means we have to suspend belief. Especially if you consider how pedophiles manipulate their victims into not telling. And I do think it likely that the monastary was home to children who were already vulnerable. Either because they were orphaned or because their parents could not care for them.
And again why the other brothers did not report it, the kindest thing I can say is maybe they too were manipulated by the guilty to believe the children were lying.
That being said I don’t doubt that some of the abuse is what probably was acceptable punishment at the time, NO I AM NOT TALKING ABOUT ANYTHING SEXUAL, THAT’S FOR THE ANTI CATHOLICS HERE, but of some forms of corporal punishment.
And in the cases that are true pederasty it needs to be remembered that one abuser can have scores of victims over the years, so a high victim count does not always translate to high percentage of abusers amongst the monks.