I would say that by the XXI century most of Europe (basically the EU and the nations mainly bordering EU nations) has transitioned to being used to Peace and using Trade power rather than Force for prosperity and to achieve its geopolitical aims, and the idea that Russia too had chosen to go with Peace & Prosperity through Trade was quite widespread.
Whatever XIX Imperialistic notions some Power Elites in Europe still have are only ever about “allied nations” (the US, Israel) with the victims being “people who are not like us” in far away lands, with the closest they get to practicing it being following the US into Afghanistan and Iraq.
So when Russia turned out to still behave as a XIX century warmongering imperialist nation, worse, against “fellow nations”, it was quite the wake up call.
I also suspect that the decades of warnings by Eastern European EU member countries about Russia over the last few decades didn’t entirelly fall in deaf ears and when some of those warning started looking like they were indeed right, this pushed the rest of the EU members and partner nations to listen to the rest of the warning coming from those nations, which accelerated the “We must stop Russia before it’s too late” reaction - I strongly suspects that an EU without Eastern European countries would have not at all reacted as forcefully and assertivelly.