The real reason is that German unification was done poorly and it benefited West Germany in a very disproportionate manner.
Most people and jobs migrated to west Germany and East Germany was left to rot.
Couple that with the fact that communism/socialism became a big taboo in Europe and capitalism's faults were completely ignored, even when it was visibly failing.
When you ban and stigmatize the left so much, people will turn to the only side that actually acknowledges something is wrong, and in this case, only the far right has done so.
"Tankies"
The irony with this is that Lemmy was founded by communists and it follows a lot of communist principles.