Ms. Bub calls it, "proving you are watching HBO"
There were two short scenes of exposition about Frank looking to get his piece of the deal back (IIRC, he can for $7M, maybe $10M). The point was there was no way for Frank to raise that much. So, he is looking for blackmail leverage while trying to retain/restart his crime empire, which wasn't a whole lot to begin with.
The premise is that all the guys at the party are in various shady businesses together. The politicians and investors are also there and perks of being in business with these guys. Gratuitous, sure but you do need a way of connecting the various business, criminal, and political players. The location of Vinci, a corrupt small town outside LA with it's entire municipal service infrastructure on the take is essential to the plot.