Edit: "local media reports earlier said the crush happened after a large number of people rushed to a bar after hearing a celebrity was visiting." https://sg.news.yahoo.com/south-korea-100-injured-people-155...
There are ways to mitigate this, like having multiple exiting edges and spacing out sets so people don't feel like they're in a hurry or knowing what sets lots of people are going to want to get to and spacing those out.
I actually wonder if there are ways to survive or at least spot a crush early. It's not something I really worry about, all things considered, but it will definitely be in my mind whenever I decide to do my Mecca pilgrimage. Though considering the gigantic crowds involved there, there's probably nothing you can do even if you spot very early signs of a crush anyway.