These situations are always complicated by the fact that people think they know how they would react, so they don’t truly prepare for the emotional and psychological gravity of the situation. They freeze, panic, then incorrectly assume their window of opportunity to report has closed. For example, a study found physicians fail to report child abuse injuries 21% of the time. Amongst regular folks, 47% don’t report known child sexual abuse. So the reality is many people fail to act, even those who are required by law to. But, since people think they would react if they saw something bad, even when some people eventually come forward after the fact, they are doubted because people mistake their half-measures for uncertainty. They look at guys like McQuearyand wonder, if he truly saw what he saw, why didn’t stop the abuse, and just beat the shit out of Sandusky.
Then you have the fact that abusers typically groom their victims, and others to accept their personal narrative. By most accounts, Sandusky was a great coach, honorable man who adopts disadvantaged kids, runs a successful charity, etc. That guy could never do something so bad. Why should someone take the word of some janitor, or some assistant coach over the reputation of a guy like Sandusky. A guy many of the people in charge had known for decades. How many of us would take the word of a virtual stranger over someone you feel you know? I would guess that is why PS didn’t initially report this guy. They trusted their own sense of judgement and fairness over an underlings.
Then couple that with they mounting feelings of guilt and complicity that arise over time as you begin to see things for what they are, and it becomes fairly clear why people consistently get this wrong. I don’t think that excuses people who remain silent, but it does give credence to the belief that if we are not actively conscious of our human frailties, we will often make bad choices.