And after a decade of planning the shutdown, stopping contracts, deferring unneeded maintenance, ... you can't just say "actually, never mind, keep them running". The plant operators themselves said it wasn't really possible or only at extreme costs.

And the politicians loudly screaming about it are mostly from parties that are responsible for the "we'll have russian gas, it's fine" policy, and didn't use the decade+ of being in power beforehand to do anything about extending nuclear, but rather often also strongly insisted the shutdown had to be done. Right until the point they weren't in power anymore and they started to blame the Greens for the consequences of their own policies.

Sure, and the reactivation of old nuclear power stations would have been instant and cost nothing. Exactly what was needed in 2022. /s

Three nuclear reactors were still running in 2022, and shutting them down was not inevitable.

That none of the energy companies went "oh, yes, totally, give us a few billions of the special budgets for dealing with the consequences of the war and we'll happily keep them running" should tell you something about the viability of that.