Eugenics lasted well more than a single decade and it had a cycling cast of characters over that time.

This would take more then a comment thread on the internet to thoroughly demonstrate to your standard.

There's pretty clear connections of more than s few conduct book authors becoming eugenicists and more then a few eugenicists becoming self help authors and self help authors revealing themselves to be white nationalists/great replacement theorists.

It's not all of them. They sit on the shelf like the cold aisle at the drug store where phony homeopaths somehow have found their way to sit next to things like aspirin and dextromethorphin. There's a similar distinction here but it might take a few pages of text to build it.

Things don't clearly map to the modern world as expected, the lines are drawn differently. Some trade unions found themselves friends of the KKK, some progressives were part of what we'd label the far right today, it's weird and takes a while to explain.

I'm glad you're skeptical though maybe I can use that to stop being lazy and write the volume.