What happened is we learned the extend of sexual abuse of minors. Estimates in the early 90s was around 1%.

Research in the late nineties revealed the actual percentage was about 9% and 10%.*

Are we over-reacting maybe but maybe not.

* I vaguely recall that in an episode of PsychologyInSeattle, a guest that was doing research into food addiction back then realized that over 40% of their patients had experienced some sort of sexual abuse when they were a child, this led them to expand their research into that subject and discover the full extent of the issue. I think the research they did put the figure for the general population at 16% but take these numbers with a grain of salt it's been a while since I listened to it.

.. however, isn't that almost entirely from people known to the child? Authority figures, teachers, priests, step-parents? "Stranger danger" was in some ways a recoil from recognizing how bad the "system" was in secret, as it relied on abuse of trust.

I think that only reinforces the fear. The old thinking was the danger was the guy in the van snatching up children. Now we assess the danger may be the father of the kid next door.

Most of that happens in families

Ofc, it doesn't mean it's any safer outside.

I mean..if it mostly happens in families that does mean it's safer outside

Families are outside too. Once you trusted your neighbor, if they are abusing their child why wouldn't they abuse yours?