Why is it that bullies forget the incident while those bullied always remember?

I've heard of this scenario always taking place:

The former bullies suddenly don't remember the incident years later meanwhile those they've bullied mercilessly remembered every single detail even decades later.

It took place on an Oprah show too. The bullied victims were paired with their former bullies. The bullies had the typical reply of ''I'm sorry I did that but I literally don'tt remember you at all''. Why do they forget the incident while the bullied always remembers?

Why is it that bullies forget the incident while those bullied always remember?
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