Long-term interest rates in core euro-zone countries are negative: How is that possible?

The long-term interest rates of the core euro-zone countries are negative: How is that possible? Why are investors not holding only money market assets? There is a twofold explanation: Financial repression in the core euro-zone countries forces insurers and banks to hold government bonds; Non-residents are buying core euro-zone bonds to diversify their portfolios by reducing the weight of the dollar.