Foreign central banks don’t really care so much about making or losing money on their dollar treasuries. They’re not currency speculators. They care much more about stabilising their currency and economy with respect to the global economy.

I don’t think you can un-pick dollar stability from its desirability. The value of fiat currencies is based solely on confidence, nothing else. You simply can’t say a currency is stable because people are confident in it, or that they are confident in it because it is stable. They are both different ways of saying the same thing. We measure confidence in a currency by analysing how stable it is in the market.