I guess I need to explain this a lot more than I previously thought (I thought this was common knowledge, sorry).

Vergangenheitsbewältigung meaning "reconciliation with the past" or "getting over what has happend" as is quite an important concept (at least in German history). It is the way a nation treats, writes and thinks about something horrible that has happend.

So in West Germany the time between '45-'68 was essentially spent saying "bad stuff happend" and "we're all equally guilty" ("Kollektivschuld", engl. "collective guilt"). With the advent of the 68er who were essentially the German version of the hippies - except less druggy and more revolutionary-y - this way of thinking ended because those blamed their parents generation and refused to take any guilt (which makes sense given that they weren't born yet). They asked questions like "What happend?", "Why did it happen?", "Who did it?" and "Why didn't you do anything against it?". The following decades saw the decline of West German right-wing thought, hunting Nazis and Neo-Nazis, the rise of the Antifa and every new party that entered the Bundestag was left-wing. After the 68er it was essentially impossible to get a job for anybody who helped the Nazis. Essentially West Germans mass indoctrinated themselves to come to believe that any step towards the right would end in another Holocaust (whether or not this is a good thing is subjective). Because of this, right-wing parties don't stand a chance in West Germany and have to constantly pretend to be "just concerned about immigrants".

But East Germany never went further than denazification. In fact the East German state systematically denied facts, forged documents, pretended people didn't exist and censored journalists(link in German, sorry) to put all the bad people in the West. The basic idea was that there was no threat from fascism because they weren't capitalist. All the blame went to capitalists, while former Nazis - some of which were even war criminals - received jobs with the state and some of which came to be quite high ranking. Because there was no discourse on the topics of racism, xenophobia, Nazism and nationalism the talk behind closed doors remained the same. Through generations it got better, but nationalist thought is more accepted in these regions and as logic dictates nationalist parties like the NDP and other right-wing parties are more popular there. It's also why Die.Linke is just a wee bit more xenophobic in the East.