I'm sorry to say that I've never heard of either Seyss-Inquart or Mussert.
But then, my family were mostly east European Jews, not west. My grandparents were originally Romanian Jews who had to adapt to Soviet rule during the war. My grandfather fought for the Soviets in Stalingrad, and didn't get bupkes
after the war. But that's how it is with the Russians - you work your back off for them, and hardly get squat.
I wonder how many people today remember the name of Georg Ferdinand Duckwitz, an attache for Nazi Germany in Denmark. He warned the Danish Jews about their intended deportation during the German occupation of Denmark in 1943, and arranged for their reception in Sweden. It is estimated that he and his operation saved almost 95% of Danish Jews from the work camps and the gas chambers. In 1971, two years before his death, he was honoured by the Israeli government who named him Righteous Among the Nations (an honorific used to honour those who saved Jews during WW2), and included his name in the the Yad Vashem museum in Jerusalem. (Yad Vashem commemorates the destroyed communities as well as recognizing and honouring gentiles who, at personal risk and without any reward, helped to save their Jewish brethren from the Nazis. The name, meaning "A Place and a Name", is a biblical quote to convey the idea of a place for the names of Jewish victims who have no one to carry their name after death).
Personally, I prefer ancient and medieval history. It's nowhere near as well-documented as the 20th century, so it gives me a lot more scope to have fun when I'm writing.
Besides, in the popular imagination, it's also a lot more colourful.