I believe Americans AND Europeans are equally educated that a high cultured society like Germany or even the US can go from a reasoned society to one where it is socially acceptable to shoot, hang, and gas women and children to death on a Saturday and go to church Sunday over just 10 short years of cultural change.

Replacement theory does not veil its genocidal final solution.
Participation in such a killing society varies from a simple hatred of certain neighbors to the actual murderers.

The change is done incrementally. I think it is a small step to go from mass shootings to organized mass shootings nationwide. It probably takes someone like Trump to normalize the unthinkable.