What has driven down long-term interest rates in the core euro-zone countries again in the recent period?

Since October 2018, long-term interest rates in the core euro-zone countries have again fallen markedly. What can this be attributed to? Increased concern over the peripheral countries? Yes; A rise in risk aversion? No; The prospect of weak growth? Yes; The prospect of low inflation? Yes; The ECB’s announcements regarding future monetary policy? Yes; The Federal Reserve’s announcements and their effects on US long-term interest rates? Yes. All these possible explanations of the fresh fall in long-term interest rates in the core euro zone seem to be valid, with the exception of higher risk aversion .