They touched on some interesting times in the last two series without actually getting to the best part, the panic in police force created by the royal commissions.
There was a Royal Commission which started near the very end of the second series (headed by Sir Laurence Street which was initially set up to investigate embezzlement by NSWRL and ARL Chairman Kevin Humphreys, after it was found he got the assistance of NSW Premier Neville Wran to help him out at an earlier court hearing. Wran contacted the chief Magistrate Murray Farqhar to help out Humphries, which he did. The 4 corners investigation by Chris Masters exposed what had happened)
This enquiry found politicians and police officers involved in far more sinister dealings and went on for quite a while. Humprhries actual hearing was swiftly dealt with, he was punished and then swept aside so they could focus on the more serious stuff about corrupt cops - Roger Rogerson beoing the key target.
By the time this Royal Commission ended, it was only a few years after that the new series of Underbelly begins.
The actions of the Street Royal Commission created a huge cultural divide within the NSW Police, the clean skins and the others who decided to tap into some more indepth and sneakier corruption antics. Since Rogerson was jailed, the whole drug trade in Sydney was made a lot more well known to NSW Police.
That is what created the attitudes seen in Underbelly 3.
There's also the story about Rogerson and Michael Drury which was quite prominent and completely overlooked.
Not to mention Warren lafranchi and Sallie-Anne Huckstepp, as well as the disappearance of model Revelle Balmain. These incidents were far greater than most of the snot in Underbelly 3.