The opinion that most olive oil sold in the US is fake and produced by the Mafia is a wobbly conspiracy theory. Olive oil is produced in many countries, not just Italy. The Mafia could not control imports from at least a half dozen countries. In addition, the production and export of olive oil is very lucrative. Selling adulterated oils makes little sense as adulterations could be easily detected. Large importers test oils and would easily spot bad product. Importing the legitimate thing is lucrative on its own, so there is no incentive to produce adulterated oils.
Yes, I believe that up to 80% of the olive oil in America is not genuine olive oil, but I do not believe that the Mafia created the scam. With food costs rising, many company compensate with those rise in costs. Olives are often imported and require a specific climate to grow. These conditions cause them to be expensive. Olive oil requires millions of olives to create. In order for many companies to continue to provide a product without creating too great of a price increase, they mix in filler oils with olive oil in order to cut their production costs, make a profit, and to gain customers. Though these methods are illegal and unethical, these companies conduct these actions to survive. These actions have nothing to do with the Maffia.
I'm not going to lie, this is the first I have ever heard of ties between Olive Oil and the Mafia. And largely the Olive Oil industry has some tight restrictions, so I would guess that if 80% was fake, there would be a harsh penalty and FDA would follow through with some fairly strong actions. Like most products sold, companies go through some rigorous testing before they are allowed to do product placement on the shelves. 80% seems like a large portion of this product being "fake".
There are numerous articles, from many different sites (with many different interests) that all agree that about 75% of olive oil being marketed in the USA does not meet the standards to be sold as olive oil. But while this "seems" to be true, I do not believe that it is all being produced by the Mafia so until I see some reliable evidence (with cited sources) about that.