> shut down fully working nuclear power plants in the middle of an energy supply crisis

Yes it is a stupid decision, but your timeline is out a little - 2011 is when they decided to shut down the power plants, the energy crisis was 2022. The amount of work that doesnt get done when you are 2/3/4 years from end of life makes reversing the decision on the day of shutdown not as easy on the ground as it is from an armchair.

In a crisis you sometimes have to go the non-easy way. They built terminals for fracking gas in record time, so I am sure they could have found a way to keep those nuclear power plants running for a few more years.