Have you heard of Fox News? It's a TV channel that runs completely fair and balanced news. Anybody who says otherwise is a weird conspiracy theorist. /s
Those elite investors can run large scale propaganda campaigns via the media that they own to sway voters from candidate A to candidate B.
Their preference is to cut candidate C (the kind that likes stuff like public housing, single payer healthcare, reducing military spending) out of the political system at a low level and let voters fight over A and B at the highest levels (e.g. president) safe in the knowledge that A and B both have billionaire best interests at heart and that voters really feel like they're getting a choice.
Which, of course, they are not: https://www.princeton.edu/~davidlee/wp/voterspolicies.pdf