Overconfidence is a huge problem. Knowing that you don't understand how the world works is important. To the extend that people believe that they can learn significant things from history, "weak evidence" can often produce problems.

If you look at the Western Ukraine policy they didn't make a treaty to accept Russian annexion of the Krim in return for stability in the rest of Ukraine. That might have prevented the mess we have at the moment.

In general political decisions in cases like this should be made by doing scenario planning.

It on thing to say that Britian and France should have declared war on Germany earlier. It quite another thing to argue that the West should take military action against Russia.