>>518559540
I suspect you may be correct with the human nature angle.
Coupled with the fact the commanding heights will tend to attract the most corruptible people into its hold, it is likely that naive optimism (or outright apathy) in the median citizen is what allows this to occur.
Ideally, one would expect people of moral worth wind up in the political arena, but that rarely happens. Meanwhile, criminal networks become entrenched over time leading to a condition where only "one of them" can be selected as a representative because the People™ become too distracted by the machinations the criminal networks setup before them. It's a natural consequence.