The video is by Veritasium titled "What The Prisoner's Dilemma Reveals About Life, The Universe, and Everything". He does a great job explaining things in a way that is entertaining and he goes into a lot of detail. This entire journal is a bit of a spoiler so keep that in mind if you keep reading.

The video: https://www.youtube.com/watch?v=mScpHTIi-kM

A lot of psychology experiments fall into the trap of limited iterations. But that's not how things work in real life. People see how other people act and modify their behavior accordingly. What may arise in a psychology study doesn't necessarily reflect real life. In this video, the focus entirely is on multiple iterations. The conclusion is that being nice pays off. But don't be a pushover. Yet also be forgiving. Long into the video, they add an interesting twist: The possibility of errors. Every once in a while, an agent's decision will be flipped. Under some rules, this error can trigger a spiral where in trying to punish bad actors both agents spiral down and both lose, even though there was no malicious intent. They were only reacting to an error.

I find it fascinating because it has some big implications in dealing with people. Punishing bad actors is important yes. Don't be a pushover as that will lead to being exploited. But people can get stuck in a cycle of constantly retaliating against one another. In that situation, both people lose. More people need to be aware of this and stop holding infinitely long grudges. Forgiveness is very important towards achieving the best outcomes.