That is a question I have asked as well.
I don’t know what the law in Pa is...but in Texas a teacher, coach, clergy person, medical professional, etc. are required by law to report even a hint of molestation to the authorities. Not just a superior.
They won’t indict him because they need him to testify. It’s infuriating, but it happens all the time in the legal system. The small fish get away if they rat out the big fish.