Its own failure
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Their failures were many, cumulative. Allowing member nations to individually add to their debt resulted in a debt spiral. Most all now carry 100 percent plus ( Germany was in best shape, now in major Recession) debt to a shrinking GDP….debt unsustainable, illegal immigration unsustainable, social programs unsustainable, tax revenues unsustainable, no resources or anything of “ value”, then the death blow, their war with Russia.
Suicide, Fools.
I see the lack of fiscal restraint as primary, in that it would have otherwise constrained so may of the other profligate behaviors you cited.