Rather like pre 2022 Russia, governments get warnings that something bad is going to happen that it would be expensive to prepare for, and put off preparing because you don't get political rewards for that.

The reason Germany didn't prepare for it was because multiple leading politicians were bought and paid for by Russia. Be totally clear about that. Former German president was working for Gazprom on the project whose stated aim was to facilitate an invasion of Ukraine at some point (which Trump pointed out, and EU politicians literally laughed at him).

The issue with the EU is that they lack the capacity for any kind of strategic thought. There are multiple reasons why but the underlying cause is that it is possible to move into local minimum where there is a very strong disincentive for any kind of change. Countries in the EU have generally been in that place since before the EU...that is why the EU was created, to limit change. It is isn't political incentives, it is a fundamental aspect of the political culture. If you also look at the stuff that has changed, this only becomes more strange (i.e. government intervention, immigration, regulations). Change is limited to preserve control.