One of my favourite Brit TV series is "Hustle".
Yeah, I know that they are glorifying and presenting in a romantic way the 'grifters' and probably things in the real world is nothing like this, but the con men from "Hustle" have a nice credo:
"You can't cheat an honest man."
And I think it is generally true.
Even if the guys from the white van are selling real merchandise on low prices under pretext that something happened and they just need to get rid of it - everybody could think 10 seconds and conclude, that either these goods are stolen or there is something else going wrong and the sellers are bunch of liars.
So, you see - the scam is possible just because there are buyers, who unscrupulously will buy anything, even if they are guessing that there is something wrong with the deal.
No matter if it is a genuine merchandise or fake.
But when it turns fake - you should remember your thoughts or intuition that probably something was wrong with the deal and that your greedy side took over.
... and now you are punished for you greed.
I am always saying that for such things to happen - there need to be two sides - seller and buyer.
If, we, people were perfect and 100% honest - such scammers would have just died out of hunger - no sell will be possible.
So, generally they feed of our greed - that's it.