After the 'fall of the wall', Europe, particularly Germany, believed that war on European soil was unimaginable, and that Russia would turn into an at least semi-democratic state, with economic ties motivating political reforms. So they stopped spending on defense, started buying Russian energy, and generally positioned themselves to their current position. (I visualize an ostrich, head in the sand, ass exposed to the air!) Here, I'm using "Europe" both to mean the collective political institutions, i.e. the European Union, and as a shorthand for the actions for the individual sovereign nations that occupy the European continent. One could say 'painting all European countries with the same brush" is unfair, but from where I sit on my side of the pond, there is significant commonality of strategic thought across the continent. Trump came along in his first term and in his transactional way, said "Europe has to pay for its own defense,' denigrating both political and strategic/military aspects of collective defense. Europe treated Trump as 'a bad dream that will go away,' and when that proved to be wrong, they're left holding the empty bag. (This is NOT to agree with Trump's approach for international/strategic/defense affairs, but particularly on NATO defense spending, he did have a point.)
Now Europe has to play catch-up. It has to spend significant resources in defense, not the least of those resources are adding large numbers of people to its military. It has to wean itself completely from Russian energy. It has to rebuild defensive alliances that are not dependent on the primacy of the US. It has to figure out how to reconcile NATO and EU as actors in the strategic space.
"A new Europe must emerge" I would agree, but (a) I don't see a clear consensus within the European countries for what that 'new Europe' should look like (look at the gains of right wing politicians, not just in Hungary and Slovakia, but in Netherlands, France, and even UK.) (b) it's not clear that Putin will allow Europe the time to figure this out. A first step HAS to be figuring out how to re-integrate the UK into European strategic discussions, without entangling UK in European social and economic nets.