Wasn't many of the reactors shut down in Europe in need of being decommissioned anyway? You shouldn't run a nuclear reactor forever and ever, and most of the reactors in Europe are quite old.
I know there are cases of decommissioning too early, or even a reactor that was fully built but not even started operation (I think Tom Scott had a video on that?), but I don't think that's the common case.
many nuclear reactors in a lot of countries also have very low yields compared to modern reactors. (for instance, most nuclear reactors in the netherlands have been disbanded because they provided little power)
I know there are cases of decommissioning too early, or even a reactor that was fully built but not even started operation (I think Tom Scott had a video on that?), but I don't think that's the common case.