I’m not sure that economies ‘can’ actually crash while running on 0 or below interest rates. I mean why crash when one can just buy more time, it’s free! Just keep on borrowing.

I think the real danger is on the other end, hyper-inflation. However, the reason this has not happened yet is due to globalization, cheap money in developped economies flow into emerging economies (China for the past decades), which is not necessarily a bad thing. We’ve only seen massive inflation in products that cannot be imported, like housing.