Certain animals, usually social species, have a sense of solidarity, morality and fairness. But even in species where this exists, cheating also happens. Both ethics and unethical behavior is adaptive.

Notably, present human society has allowed tremendously unethical leaders to rise to the top of given nations and organizations despite the average person usually having basic ethics.

Wouldn't politics be precisely a sector of human endeavour where being amorally unfair is an advantage to achieve your goals? If the other guys are lying, and everyone is gonna believe everyone's bullshit anyways, might as well get good at lying yourself.