Issues with nuclear like fallout from Chernobyl still leading to contamination today in German or bad handling of nuclear waste at the Asse II mine have been a topic in German society for a very long time. The climate crisis picked up as a topic only really in the late 90s. That explains the first nuclear exit plan in 2000.
The current exit from 2011 was a direct reaction to what happened in Fukushima.
I mean even today you still have plenty of people and company that think that there is still a lot of time before more action must be taken against climate change.