You are missing the point; titling the article "The Scam Wall Street Learned From the Mafia" is a rhetorical device used by the author to illustrate the criminal nature of what went on and draw parallels to activity that is commonly understood by the average person to be unethical. The author isn't trying to suggest that these banks literally learned this from the mafia.

"the crimes the defendants and their co-conspirators committed were virtually indistinguishable from the kind of thuggery practiced for decades by the Mafia, which has long made manipulation of public bids for things like garbage collection and construction contracts a cornerstone of its business."