"Mafia" seems a strange and prejudicial word to use here. "Less than 2% of the anonymous ownership accounts that can be tracked on Bitcoin’s blockchain control 95% of the digital asset" - at first I thought this was really astonishing. Now, I'm not so sure. My first interpretation was that 2% of bitcoiners have 95% of the bitcoin - but now I wonder how many addresses a typical person has. e.g. If I create an address…
My impression was that they don't and that a lot of transactions are actually settled within the exchange using good ol' relational databases and not the blockchain.
If that's the case, then all of these people will get lumped into just a few exchange controlled adresses, which will give an exaggerated impression of concentration.