Probably at the bottom of it is some prudishness. But the primary point is that Moore did a lousy job of combating the accusations. It is a very complex situation and if the current climate of alleged sexual harassment executions didn’t exist then Moore may have won. Everybody has a past. Sometimes it bites you on the a$$. It is how you respond that is important and Moore just wasn’t good at responding.
I am not as old as Moore but I lived in the South in the 70’s. In my experience it was very common to have younger girls dating older men many with their parents blessings and in some cases encouragement. Went out with two myself that were “jail bait”. But I can with a clear conscience say I never laid a hand on either of them. One was very willing and able but no way I was going there.