The researchers studied how interconnected banks in Germany could be at risk if one bank fails to pay back its debts. By looking at the relationships between banks, they found that without a safety net, one failing bank could cause problems for many others. The safety net, which acts like a financial cushion, reduced the risk but did not fully eliminate it. The study shows that without this safety net, up to 15% of the banking system's assets could be at risk if a single bank went under.