The Wikipedia article on the Human Biodiversity Institute cites the term human biodiversity as becoming a euphemism for racism sometime in the late 90s and Marks’ book is from 1995, so there was apparently a pretty quick turnover. Which makes me wonder if hijacking or if independent invention. The article has a lot of sources, so I might mine them to see if there’s a detailed timeline.
Fascists were always cringe. Himmler was a weird occultist. Goering was a drug addict still high on his glorious from World War I. Hitler was a profoundly lazy man with terrible taste in art. There were normal fascists (there had to be), but the leadership was always cringe. Unfortunately, being cringe doesn’t stop a movement from killing vast numbers of people.