You really think Cruz or Paul will win the primary with the backing of the Kochs? We shall see - I'm not as convinced that money rules the day like you do. This will be a good test to falsify your position if neither of these two win the primary, as they are the two candidates backed by the Koch fundraising network.
The Kochs aren't the only oligarchs buying elections. And all the campaigns are paid for by the wealthy elites, so that they own whomever wins. That's how they insure that the game stays rigged.
Also, regular people can't run for high office. And those who can are politicos who have long since shown themselves to be the servants of their wealthy donors. Congressman, senators, governors, these are the pool of candidates, and they are already proven servants of the rich. And even if they were not, neither party would run them. Because both parties get most of their money from the oligarchs.
The whole show runs on money. Only those who are bought and stay bought get to play a part.
By the way, the Kochs main focus has been on state and local elections, lately, where they have personal business interests. There they can buy off the politicians and necessary officials to circumvent environmental and labor laws much cheeper than they can at the federal level.