I'm out of my depth in economics here, but perhaps one reason it's
different when there's a bubble inflating rather than bursting is
*information*. When the housing bubble or the dot.com bubble is
inflating, it's fairly easy for people to know that it's inflating, and
thus where the new jobs are. People from hundreds of other parts of the
economy know that there are jobs to be had (and pretty good investment
opportunities to be had) in housing (real estate, construction, selling
mortgages) or in dot.coms (software, selling development tools,
investing in startups).
When the bubble pops, the information about where jobs are is much
more diffuse. It's not "go west (to the Bay Area) young man," but
rather "go back wherever you came from and see what's available."
And here is comment by Russ Roberts.