The leader of the centre-right opposition party the Christian Democratic Union (CDU) was roundly criticised for the ostentatious arrival, both for flaunting his wealth and ignoring concerns over the climate crisis. Far from being chastened, however, Merz doubled down.
Technically it was both of them. Quitting nuclear power was decided by a red/green government in 2000. Mind you, they actually had some decent arguments back then; our reactors were approaching their operational limits and extensions were becoming increasingly uneconomical. The nuclear phase-out was expected to take until late 2024.
In 2010 a conservative/liberal government decided to put the nuclear exit on hold for 8 to 14 years (depending on the age of the reactor), then reverted their stance after the Fukushima nuclear incident in 2011. The nuclear exit was completed in spring of 2023.
A notable difference between the parties was that the red/green plan was designed to let the reactors “run out”. Germany was contractually obligated to buy a certain amount of power from each power plant and these contracts would be allowed to finish without being renewed. The conservative plan instead set a hard time limit, leading to a series of lawsuits as the plants were shut down before they could deliver the agreed amount of power. That little stunt cost us about two and a half billion Euros.
Technically the nuclear debate goes back to Kohl already, because of how old the reactors were. Also, the Greens had a tiny percentage in the SPD led government back then and were not planning on using coal as substitute, like the Union eventually did, but to increase renewables. The Union eventually also killed our solar industry and all their jobs, while they saved & campaigned about the jobs of coal miners. It’s just an unfunny joke at this point.