It's not, really. You can actually see that both nuclear and coal have been replaced by wind and solar in Germany. The issue about Hambacher Forst is politics and political lobbies. The area is owned by RWE since the 1960s and the open pit mine next door exists for much longer than the decision to get out of nuclear. It's simply convenient to blame this on the "Atomaustieg" as part of a lobbying campaign.

It's also interesting that nobody was saying that the Atomaustieg was responsible for increased coal use in 2020. Because it's only last year that was an exceptional year, which saw a uptick in coal vs wind.