Why is it the case that some humans still do not seem to get it?

Most people don't care how they get what they want. If it's violence, great. If it's from making the pie bigger, great. A few other things persisting violence:

1. I think violence is viscerally more satisfying - not only do you get a bigger slice, someone else gets a smaller one, and we're primarily concerned about relative slice size.
2. The pie getting bigger threatens the relative slice size of all existing slice holders. In a zero sum pie, they merely have to play defense to keep the same proportion of the pie. When the pie is getting bigger, they have to play defense and offense.

I'm curious what might have caused this scale-tipping

I believe it's the coercion groups seeing freedom groups getting more of what they want. So long as we don't have a monoculture, cultures compete and it's culture-see-culture-do

and if we believe they actually did tip.

I believe it did tip more recently, but I don't think there's much preventing it from tipping back if say China ends up being the world superpower.

I also don't fully buy that coercion is under all circumstances incompatible with growing pies. There are many factors that cause a pie to grow or not grow. Freedom is an important factor, and perhaps the simplest and most powerful factor, but not the only factor.