Capitalism and corruption
One always goes with the other, similar to how communism and authoritarianism always go with one another. And for the same reasons - because both systems have their flaws, and those flaws lead to negative consequences that come along for the ride.
In the case of communism, because once you get beyond a community the size of "everyone knows everyone else" or at most one Bacon number distant ("everyone knows someone who knows everyone else") it just doesn't work and needs to be forced on a population against their will.
In the case of capitalism, when your whole system is based on private ownership of means of production and the profits derived from them, then those who hold public office are defacto private owners of the means of producing political outcomes, so they profit from "political favors" exchanged for money or other goods/favors like in any other market.