It is not at all that clear to me. The thing with psychopathy at least. We have about 15 per cent of psychopaths up there (compared to the societal average of 1 per cent). Contrary to the general myth, even most high-ranking Nazis were paper-pushing conformists rather than psychopaths like Oskar Dirlewanger. Would the Amerindian society fare very differently?
First, the groups are relatively small. 100 to 150 persons at most, not a whole country like Weimar Germany. Given high mortality and the fact that women didn't become chiefs, your purely numeric chance of becoming a chief was reasonably high if you lived to be 35 or so, just from the fact that you lived and had a lot of valuable experience (in an illiterate society, the elders are a vital knowledge source). Also, this was a fission-fusion society: smaller groups separated under their own chiefs, went their own way, then came back and fused for some time again. Which opened some positions of "junior chiefs" to prove themselves.
Too much eagerness to engage in violence will likely get you killed at a younger age. Serious injuries amount to death in the forest, and even many lighter ones. If you really "optimize for max violence", odds are that you will be killed soon. You cannot win every battle, and some of the deaths described by Valero were basically murders from behind.
There was certainly luck involved, but also a mix of other attributes, including your ability to fight. But it is not clear to me that psychopaths would have a decisive advantage. It is fundamentally physically dangerous to be a violent psychopath in a society with zero healthcare.
An interesting read on this topic is the very book being dissed in the article--Napoleon Chagnon's "Noble Savages". According to this article, Chagnon met the Yanomamo in a state more exposed to our civilization, but even then many of the high-ranking men come across exactly as I described above: charming when they want, but volatile and gratuitously violent. Two episodes from the book stand out in my memory.
- A chief encounters two young men from a rival clan. They are nervous because of this man's reputation, but he calls out to them and offers them food, charms them and puts them at ease. Then he walks behind them and kills them. In his opinion, this is hilarious.
- A man suddenly believes his wife has cheated on him. He drags her out by her hair, punches and kicks her head repeatedly. Chagnon is aghast and almost intervenes. I don't recall whether the woman survives.