I think what is important to keep in mind: Merz is on the conservative, pro-economy side of the conservative party, whereas Merkel is not. She has a background in science. She never liked Merz.
Merkel dumped nuclear after Fukushima simply to improve her electoral calculus. As in everything she did, there were no long-term concerns. Yet to her defence it has to be stated that nuclear energy in Germany was just not economically feasible anymore at that time (when gas was still cheap, wind and sun cheaper, and burning coal was not yet frowned upon). Also, Germany had shut down their own uranium mining long ago.