What Drives Eastward Expansion?

A key moment in this history of the EU's borders was their massive expansion beginning in 2004 with the entry of former Eastern Bloc countries. The result at least until recently seemed to be these intensifying conflicts between Brussels and countries like Poland and Hungary that were pursuing socially reactionary, illiberal policies and authoritarianism. What drove eastward expansion and why did it ultimately play out in such a contradictory way? And then what does this new found European unity against Russia led very much by Poland and the Baltic states though not of course by Hungary mean for those tensions? I think one of the unfortunate consequences of the war has been the rehabilitation of some of the more unsafe, very political actors in eastern and central