Germany can't wave a magic wand and switch off Russian imports overnight. But they did just commit a few hundred billion to accelerate their plans to get rid of coal and gas based generation. That's a direct consequence of the Ukrainian situation. Like the US, Germany was overly depending on cheap gas until recently. Now that it has to import the gas in liquid form from the US (and a few other places), it's going to be a lot more expensive. Hence hundreds of billions to cut their dependence on the stuff entirely.
Regarding nuclear in Germany, I think you are a bit short on the facts. Nuclear in Germany was always pretty minor. What little they had is now nearly gone. During the same time, they cut coal generation from 47% to about 25%. Gas grew a bit during that time but is still smaller than their remaining coal generation and even the amount of coal capacity they got rid off. Coal is going to be gone by 2030 according to the latest plans. Indeed cheap Russian gas was part of this plan until recently. But those plans are shifting rapidly now for obvious reasons.
Regarding nuclear in Germany, I think you are a bit short on the facts. Nuclear in Germany was always pretty minor. What little they had is now nearly gone. During the same time, they cut coal generation from 47% to about 25%. Gas grew a bit during that time but is still smaller than their remaining coal generation and even the amount of coal capacity they got rid off. Coal is going to be gone by 2030 according to the latest plans. Indeed cheap Russian gas was part of this plan until recently. But those plans are shifting rapidly now for obvious reasons.