It was already decided in 1998 to phase out nuclear power under the SPD–Green coalition. They passed the Nuclear Exit Law in 2002.
It’s mostly the Green Party’s fault, as they have been vehemently anti-nuclear since their inception(1970s).
Why do you think that in 1998 Russia was not influencing Germany to use its gas?
Moreover, Russia and its coopting of the German Left and Greens is well documented.
Gerhard Schröder, chancellor 1998-2005, is well known to be best buddies with Putin and later (three weeks after leaving office!) worked for Gazprom. He is nicknamed "Gas-Gerd".
Schröder also famously called Putin a "true democrat".
Ok. Soviet influence operation.