I should think that's because there was nothing about the listing itself that broke any rules.  The fact that someone said they had been scammed by the seller is not something a bot would be able to check, even if bots were actually any good!

What was interesting about the article was the implication that it was the classical ad nature of the listing that was the problem as you can't pay through checkout for those.  We all know that it's not the nature of the ad but the category that determines how you pay and hence what protection you get.

I don't like people being scammed but those buyers have to take some responsibility for checking exactly what protection they do, or do not, have when buying vehicles on ebay.