Regardless of any slope in the tunnel, eventually you will reach a point where you can't move forward, so could we maybe start using our brains in situations like this and just stop and wait instead of trying to push the people in front of us(who are presumably stopped for a reason) forward?
We get in traffic jams all the time, and we don't just try to push the car in front of us forward. You don't just go up to people on the street and push them in the back. It shouldn't become culturally acceptable to do these things just because you are at a sporting event or a rock concert or a religious event, and if we as a culture place so much importance on those things that our every day rules of behavior and what is acceptable go out the window, maybe we should take time to reexamine our priorities.
None of this is to put the blame on the victims or reduce the responsibility of the authorities in charge, but could we admit this is a much more complex problem than 'this is the fault of the cops that kept sending people in when it was full'.
This is a giant multivariable problem and there is more than enough blame to go around. Starting with the fact that people thought it was a good idea to design a sports stadium like a fucking prison or that there is such a cultural importance placed on tribal identity related to a sports team that fans of separate teams weren't even allowed to use the same entrance or the same stands.
The authorities fucked up in opening the gate to let people in faster and then lied to cover it up. They fucked up in designing a stadium that was completely incapable of dealing with the numbers of spectators and not doing anything to help the rush like open the gates earlier or send people to different sections instead of allowing everyone to rush into those two.
Some part of the blame also rests on the people who though it was acceptable to push people forward just because they were in a crowd and anonymous.