Most of their voters haven’t experienced that regime as adults. It’s been gone for 35 years. It’s a reconstructed identity for them, if it’s anything at all.

with its predecessor extreme right-wing parties, DVU and NPD, who were able to mobilize votes in the 90ies and 2000s.

It was a militarized society and denazification didn’t go far within the military, because a lot of men were exposed to right-wing/Nazi propaganda latest during their compulsory NVA drafts.
A strong gender (and education) divide still marks the AfD vote, and it was the same

There was a movement of women from rural areas to cities even in the DDR, caused by state efforts to get women into higher education who would otherwise not have studied. Most of them stayed in the cities. I wonder if anti-fascist attitudes were generally more prevalent in the female DDR population.

Certain parts of the East CDU would happily coalesce with the AfD though, and it happens.