It's easy, give it the time needed for the people to forget the sting of the bad things and they will do it again.
Look at kids, they will be told not to do something and yet they will go right out and do it.
They do not know the sting of getting hurt from what ever it is.
Once they have felt that sting for themselves then they will know not to do it.
But if that fades or if the kid is not that bright, they may try it again.
This is one reason the atrocities of war must never be forgotten. And NEVER be hidden from the public. It is the only way to avoid repeating it.
Follow the money and resources and it's easy to see how it repeats itself and how it can be extremely predictable. It's not exactly as predictable as a steam engine, but certainly close enough.
One of the more interesting findings of an extensive study of South African tribes was that every few hundred years all the tribes would put aside their differences and attack the most vicious tribe among them driving them almost to extinction. This was entirely predictable because it only occurred when that tribe became large enough to become a serious nuisance and threat to all the others.
probably the best (worst) example is large scale: like genocide - Europeans capturing of North America and decimating the Native population; Germans seeking to dominate Europe (and the world); ...I'm sure there's many other examples!? (N.Korea? China? Russia? to name a few)... and the beat goes on...
Its a big sucking sound coming from the others side...