They understood full well. The EU has a shared monetary policy, but no shared fiscal policy. Fiscal policy (!speculation alert!) is the next step, and will go a long way to avoiding another crisis.
Or it may work to collect the remaining unbroken eggs into one basket. Maybe centralization is not the solution here. Europe has benefited from so-called "disunity". It made economic and scientific (and social) development possible, with no one political entity able to oppose it outright.
