Going out on a limb here...
I was active duty when the Berlin Wall fell and later when the SU broke apart. In our main squadron breakroom where officers and enlisted mingle, we watched Berliners climbed on the Wall, partied, cried, sang, and some hammered away at the Wall for souvenirs of an era. I played tourist in East Berlin once and saw the difference between the two sides and I wished I was there to share in the celebration. Anyway...Just about everyone in the room cheered and some declared the Cold War over. There was a senior master named Dorr who was a second generation German emigre and he said he can retire happy. Sure, I was happy for the Germans but I was too cynical about Russia. Of everyone in the room, I was the lone dissenter.
I think the MAIN reason why the Euros were so willing to trust Russia is because overall, everyone was tired of the Cold War. The constant vigilance of the people from leaders all the way down to the ordinary townsfolk, the expenditure of some of the nation's finance towards defense, the nearly weekly dour news about arms reduction negotiations, and so on and on. I easily extrapolated the release of tension tenor of our breakroom to how nations must have felt, and I do not blame them one bit. With the Soviet Union, Russia was geopolitically enormous, so everyone, from Europe to Asia to the Americas, convinced themselves that a geopolitically smaller Russia must also mean a commensurate weaker power. What is happening in Europe today should make it clear that the Cold War is NOT over. The weapons actually multiplied from nuclear warheads to economics to now -- energy. They multiplied because the trust, and even the faith, multiplied. Now, we have to pay to consequences of that misplaced trust. You are correct about the pain that it must be suffered. Like it or not, the vigilance about Russia, and China for that matter, must return.