they did, but slower than expected and many invested lot more in Gas powered centrals... because gas was cheaper and much better than coal
The Ursula von der Leyen is actually wrong, only 4 countries in Europe reduced the nuclear: UK, Belgium, Sweden and Germany ... As she is German, she have a skewed view of the problem
So UK reduced nuclear because they were OLD and expensive, they were using outdated tech and had little power compared with modern nuclear stations
Germany also had some older centrals, but decided to kill all of them and replace them by gas centrals, as it was expected that gas was cheaper than nuclear and solve the population anti-nuclear stand. Notice that gas was cheap because it was Russia gas... renewable were given less priority, while solar actually increase a lot in Germany... but it is not efficient as in Spain and during winter is less efficient. Many wind projects were postponed or got local resident opposition.
Belgium started to shutdown some nuclear centrals, but since stopped exactly due to energy crisis
Sweden closed 4 obsolete nuclear, they were too expensive and old and they had enough renewable to compensate
All other European countries kept the same nuclear or even increase it a little. Also notice that France had planned maintenance for several of their nuclear plants during the time that Gas price skyrocketed, so they couldn't even compensate and in fact required more use for gas.
What she may say is that most of the investment went to gas centrals, that now are a problem... some of that could have been allocated to new nuclear, but the same could be said to add more renewable and storage (hidro, weight lift, spinwheels, battery)
New gas central kept being built, as they take years to build, but now gas is not cheap russia gas, but expensive US and middle east... with Russia blocked and now war in middle east, everyone that bet in gas is paying more for their electricity
During that time, Spain, Portugal, Denmark invested in renewable and they have lower electricity prices. Even UK invested in renewable and what have lost in nuclear is more than compensated by renewable sources:
https://app.electricitymaps.co...
on the other side, itally, a country with huge renewable potencial, invested very little on it and mostly on gas and now they see how wrong they were
https://app.electricitymaps.co...
compare that with spain
https://app.electricitymaps.co...
Notice that spain also have plan to shutdown most of their nuclear centrals, as they are more expensive than renewables
So the problem here was that nuclear was phase out in some places a little to early and too much investment was done in Gas. South europe countries can and should invest in solar, Italy, Greece can have huge solar potential that is being wasted (talking about home setup and industrial rooftops, that should be enough, no need for mega solar projects). Wind can be used in many places. offshore wind too. Tidal needs more research, but can have a huge potential in all coastal countries and finally, storage solutions, as renewable works much better with storage (See Portugal usage of storage, getting cheap solar from Spain during day and selling storage hidro on peak usage for much higher prices: https://app.electricitymaps.co...)
If you invest in solutions that require other country fuel, you are always dependent of those sources. if you instead invest in our own energy, you get short term higher prices, but them long term lower prices
Another problem is the infrastructure, Spain and Portugal invested hardly to modernize their electric infrastructure and are well connected. Sadly France is blocking better connections to Europe, mostly to protect their nuclear business from cheaper renewable energy... but many countries are still islands of power, build around nuclear or gas centrals and not in disperse energy production. Italy is a great example of this, many small electric islands that make renewable investment harder as the grid is not prepared. So again, instead of gas, many countries should have instead invested in upgrading their electric network to help renewable to work better.
As for the EU commission, they should push for this network modernization, push a lot all EU country electric inter-connects to help energy flow where it is needed. They bet "all in" on Gas, i hope they don't think in bet "all in" on nuclear. Solar and wind are already cheaper than nuclear and most of the time, cheaper than gas... gas and nuclear are useful when there is no wind or sun, but that is also why OTHER renewable sources should get more attention