The thing is, the antisemitism of the holocaust era didn't cease to exist once the war was over. All of those antisemites didn't become pro-semites, so it's always been there, bubbling away, and now they have a "cause" to nail their hatred to, and they have grasped the opportunity with both hands - they get to openly hate Jews and be "on the right side of history" (if they're on the left or basically just hard of thinking).
I was in Vienna recently, where the only place I witnessed any kind of security, apart from the airport, was outside the Jewish museum, where there were armed guards. I also visited the Sigmund Freud museum. I'm ashamed to say I didn't know how much his family had suffered at the hands of the nazis. Something I read there gave me pause for thought - so many wealthy, industrious and accomplished Jews fled Germany and Austria (they were lucky ones - they had money and contacts). When the war was over, they were not encouraged to return - antisemitism was still rife. Neither was Freud's legacy as the father of psychoanalysis recognised until the 1970s, and that was largely due to pressure from the USA, because of deep post-war ambivalence in Austria toward his Jewish-rooted legacy.
What is happening now, or rather, being allowed to happen, is shocking but sadly not surprising.