That's what they do in Germany. They teach it as a unique thing that can never happen again... which leads people to never question whether it could happen again... which may lead to it happening again, because any sign that it was happening again would be dismissed, because "it can't happen again" is drilled into people.

The default attitude of any human is to support the status quo, but you'd think Germany in particular would do a better job of changing that default with education. It seems like it doesn't.

Obviously, if someone was doing another holocaust, it would be in their best interests to make you think the very notion of more holocausts was prima facie completely absurd.