We could keep the economic system in place that allowed the oligarchs to get so powerful if we simply figured out better ways to tax them to limit their wealth to a stupid but not globally-stupid level. Universal healrth care and other social nets, ending the insane wealth inequality and restoring it to merely unhealthy levels. Put laws in place to break up media and political influence (i.e. money into politics, e.g. Citizens United).
They could keep a decent portion of their wealth and we could make things more fair and better for everyone.
But at this point, I think it's going to take radical change to break their hold.
I wouldn't downplay external influences, but I certainly say this is primarily an internal event and nothing new, but a combination of how the country was founded plus evolution over the decades to make it worse and worse.
My main objection to the submission is the idea that foreign influences played no role at all. And the submitted idea is ridiculous on its face.