Afaik if you're talking about what happened in korea, there were still walls that they were bound by. Its the same as for concerts; they're always outside, but because of the barriers they put up, people can be crushed

The people at the back can't see what is going on at the front - This causes more and more people to join. It increases the density of the crowd which forces more weight onto the people at the front.

This weight is what crushes you - It squeezes the oxygen from your lungs and makes it incredibly difficult to breath.

Ripple effects. It just takes a little bit of panic in one spot and people try to leave +trying to make more space and than it spreads out in every direction like throwing a stone in water. That leads to other points of too little space and therefor panic. So it just spirals out of control. There is also confusion and panic why some people trying to get away.

If everyone was rational, everyone would take their arms down. Take as little space as possible and try not to move anywhere. and it would be over in 10 sec.

Similar things have been happening in Salem, MA for over a month. The streets are just too narrow to handle a crowd of 100,000 people each day, not to mention vehicle traffic (which the town has been actively discouraging by closing streets and asking people to use mass transit).

There was also the Traviswold thing that happened a few months back. The concert venue was oversold and overcrowded, and people got suffocated & trampled.

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You ever get stuck in traffic? You step on the brake, right? What would happen if you didn't? You'd tap the guy in front of you, who might hit the brake, or might hit the gas and hit someone else, or might hit the brake and still hit someone else. That's how you get a 4 car pileup in dead stop traffic.

When you're in a human crowd, though, you can bump and push people in all directions. And they'll move, too. And all of a sudden, people are just pushing forwards to escape the pushing behind them

It's a plethora of reasons.

First: The people at the back want to see what's on the front, so they push forward. The pushed people unintentionally push the people in front of them, and before you know it, you have a whole crowd that turns into human liquid. The more in front you are, the worst is going to be. Imagine it like a wave where the bit that touches the shore is the first one to curl and break, and the rest crashes on top.

Second: The people at the front are trying to back up from what's on the front, so they push the people behind them with their backs. This type of crowd surge is usually the easiest to trip in and fall backwards. If you fall, the chances for survival are very slim. Anything from asphyxia to broken bones piercing your organs can easily kill you.

Third: There are lots of assholes, or people that think they know better. If you start pushing forward, and the people in front yell at you to stop, STOP! Listen to them. It's not funny, the crowd isn't there just for you, you wouldn't like someone to do that to you, and if you keep pushing, you will be complicit in killing people. Granted, you're not pushing in order to kill them on purpose, but your actions will certainly end the lives of many others.

Fourth: People are so tightly cramped that their lungs become unable to expand properly, which usually leads to shallow breaths that inevitably result in people getting passing out, or getting completely asphyxiated. If your four corners are touching someone else, you're already in danger. Always make sure to have at least one corner free of people.

Fifth: People trying to go against the push of the wave. If there's a wave, the best thng you could do is allow it to take you, and DO NOT FIGHT IT. A lot of people in their justified desperation try to turn around, and fight the massive horde of liquid people coming at them with full force. You're not going to win against thousands of pounds pushing against you. Think of it like a Tsunami, and someone trying to stop the insane amount of pressure coming at them. People will accidentally knock you down, knock you out, or get you cramped against somebody, or someone else.

Sixth: Lack of crowd control from the event organizers. This is laziness and negligence on their part. A lot of disasters could be avoided if the guys in charge controlled the flow of people, and prepared for bigger crowds.

Seventh: Pray to whoever you pray to that there isn't a wall at the end of the wave. The wall is ALWAYS going to win. People are getting absolutely crushed, and the wall won't budge. Broken bones piercing organs, asphyxiation, and getting knocked out are the most common ways to go here.

Here's a great comment from years ago explaining in great detail how it happens. Please give it a read if you want know more, but be forewarned that it might be a little too intense for some.

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To add to the other points, here's a visual demonstration of human fluid dynamics. https://www.reddit.com/r/gifs/comments/qp3rsg/fluid_dynamics_of_an_overcrowded_venue/?utm_source=share&utm_medium=android_app&utm_name=androidcss&utm_term=1&utm_content=share_button

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