This explanation just reworks the question into one of why western interest rates are so low.

Western central banks can't raise interest rates above the lower bound without triggering unacceptable unemployment or even deflation. Indeed, the highest safe rate has fallen in the wake of every recession.

To me, this suggests major structural problems in the western economies. It's hard to think of a single explanation that applies to all (pre-pandemic) zero-interest rate western economies, however. The economic foundations in Australia, Canada, the UK, the US, and the EU are different enough that there is no obvious single structural fault common to all of them.