I'm sure stuff occasionally slips through, especially when they don't use the term "Nazi" in the description.
Ebay's official policy on Nazi memorabilia can be found here (and it appears that postcard may be in violation):
I remember when they implemented it. It might've been a decade or so ago. There was a fair amount of butthurt. Prior to that, eBay sold a lot of Nazi stuff, original and reproduction.
Right.