It isn’t nostalgia, it’s foresight.
They expect the EU to dissolve completely any minute now that the UK is leaving and I read several other countries are considering it as well.
There have been sporadic calls for a return to the Deutsche mark over the years. In addition, Germany has been repatriating gold held by foreign banks, including in the US.
Given that 2008 article by Ambrose Evans-Pritchard that illustrates the intent of EU elites to cause a crisis with the euro in order to engineer a big power grab, it is not surprising that people want to be ready for that.