what I am saying is there doesn't need to be an actual "trigger". When a bubble forms, it by definition has to end eventually. Sometimes that can be just "no new suckers left to enter the bubble" Simplified of course.
Seriously, if someone in US in 2006 was saying "how could house prices ever fall? what would the trigger be?" would that be persuasive? No, there was no trigger, prices started falling there as it was a bubble. Bubbles can just end. then they cause destruction.
