Actually, in this case Bezos has shown a resistance to corrupt influence BECAUSE he's a billionaire. (I'm not disputing the list of corrupting influences DUE to being a billionaire, just pointing out this particular case may have the opposite)

Having a larger number of respected media outlets could help. Having news and money separated is great, but hard to implement. (patches welcome!) . Having media outlets that no individual or small group can control, regardless of their money, also good but tricky.