Those countries may not have hit "herd immunity" yet, that's the point. How do you explain Sweden? I know France has still considerable restrictions and mask wearing etc. Can this be explained by changed in human behaviors in those states above?
I doubt it.
Something else is happening, I think.
This thing starts, and looks bad, so we shut down and suppress it, but then start to reopen and it comes back in full force. And then, it slows down again, as with Sweden. No real changes in human behaviors of consequence.
I guess you could claim the protests largely dissipated.
Area under the curve ...?