Toxic behaviour online is a consequence of anonymity removing the repeat game that makes people behave well in person.

It's because you have one identity. And if you stiff them, then life is a repeat game and that's not going to work out well for you. But in a digital world where you can be anonymous and show up in different ways, I think the incentive to act like a good citizen can be a lot less, and that causes a lot of issues and toxic behavior.