What it meant in practice was that as long as a national government was committed to a fiscal austerity plan — tax hikes plus spending cuts — the ECB would commit to potentially unlimited levels of bond-buying in order to prevent its interest rates from spiking. In one of those magical moments of monetary policy, the existence of the commitment meant Draghi never really had to test it. Speculators stopped betting on default and collapse, governments wrote austerity budgets, and interest rates steadily declined.
The result was that banks that owned eurozone government debt were saved, and so were institutions around the world that relied on the European banking system not collapsing. All in all, a job well done. Meanwhile, politicians got to take credit for keeping their countries in the Eurozone and for falling interest rates while pushing the blame for unpopular austerity policies on Draghi and German Chancellor Angela Merkel.
People left behind
The only problem is that the downward spiral didn't start with high interest rates, it started with bad economic conditions. When people don't have jobs, they can't pay taxes and that puts pressure on government budgets. But the budgetary consequences of sky-high unemployment are only scratching the surface — the real problem with sky-high unemployment is the widespread human misery.