Eugenics received widespread support pretty much until the truth came out about the treatment of the Jews in Germany, which is when the supporters suddenly woke up and understood what the realization of those ideas inevitably leads to.

But that truth was not fully revealed until 1945 with the liberation of various concentration camps. Until then, most details and rumors about the camps was dismissed as idle propaganda because noone believed the reality could possibly be so shocking.

In 1935, little was known about what was going on in with the Jews in Germany, and most of the really extreme ideas were not implemented yet. What discrimination occurred was not unique in Germany, as most nations of Europe practiced some minor forms of tacitly-approved anti-semitism

Antisemitism is different than eugenics in fact, if not in spirit. Eugenics is the conceit that elites amongst the population should pick the winners of this generation in order to 'improve' the next. Antisemitism is saying that there's something in the nature of Jewish people that is bad for society in general.

One is about picking winners; the other is an opinion on how to pick them.