Germany literally just shut down their existing nuclear plants and replaced them with fossil fuels.

That's completely false.

responsible for like 1/8 of Germany's electrical production

More like 2-3%

it wasn't a cost decision

Not exclusively, but the high price of nuclear is one of the main points in the decision

the graph at the top shows the growth in Germany's installed wind capacity in Germany leveling off

Because the graph stops in 2022. The growth now is accelerating and even more so for solar power which OP conveniently does not show us

https://strom-report.com/photovoltaik/