Arrogance.
The brothers know that their money and power will shield them from being directly prosecuted.
They operate like an organized crime syndicate does: Buy influence and power by corrupting everyone and anyone you can. Bully and threaten the rest of them into line. Get away with what you can until you get caught, make sure the dirty deeds are well enough insulated away from you, pay the paultry fines, learn your lesson from the setback by concentrating on how to do the dirty deed again without getting caught, then look for more opportunities to exploit outside the law.
This gives the brothers the edge they need over their competition. They're willing and able to go where others won't because they lack the morals, ethics and decency their competitors are bound by.
This either forces their competition to play by the Koch rules or get out of the game entirely. Either way, the Koch brothers win.
