The human and economic toll of the COVID-19 pandemic have been most extreme in Italy and Spain, so it is no surprise these two states are the main voices in favour of corona bonds. Economists Jakob von Weizsäcker and Jacques Delpla initially proposed eurobonds in 2010, arguing that jointly issued bonds, by reducing the borrowing cost for all states, could prove an incentive-driven and durable method out of debt crises, and ultimately help strengthen the Euro as a reserve currency. Many economists have also advocated for modern monetary theory (MMT) based policies as the most robust approach to an economic depression, and arguably corona bonds fit this way of thinking.
MMT encourages the creating of new money through central bank monetary policy and government deficit spending, to maintain high levels of employment and balancing subsequent inflation with taxation. A sovereign currency itself is a unique public monopoly that can never run out, so there is no default risk, and unlike a household and a business a country with its own sovereign currency can operate its budget in a way that's different from normal small-scale budgeting. But it's not just the hardest hit governments that have taken this stance, many economists have placed themselves on the side of deficit spending as the best way to overcome this extraordinary prolonged economic depression the world now faces.
Furthermore looking back at the history of the EU such jointly issued bonds are clearly a measure that has worked in the past with more than a dozen community bond policies being issued to private markets by the European Commission since the 1970s. Such measures have a history of being successful in the EU, as well as a history of being fully repaid. A misstep at this next stage in European financial decision making is widely considered to threaten the very existence of the European Union, for example Italy has openly threatened to “do it alone” if the EU fails to cooperate on this issue.