Here we see one of the general "Alpha male attitudes". It's very physical in its symbolism: Chin up, chest out, trying to give the impression of being bigger and taller than other men, also straight back and arms "making handles" at the waist. It's obvious that these two guys were showing off as best they could, especially the one to the left: Benito Mussolini. However, it was the shorter one - and he really was very short! - to the right who held the reins, so to speak: The Italian King Victor Emanuel III who played a decisive role in bringing Mussolini to power (1922) as well as removing him (1943). The German friend and associate of Mussolini, Adolf Hitler, positively abhorred this king for being very short as well as down-right ugly. Still, king he was, which gave him a sort of alpha-birth-right, decided by history and politics.

Before the 1990s the terms Alpha and Beta were primarily used in animal ethology, maybe especially in apes. After the publication of Frans de Waal's book "Chimpanzee Politics: Power And Sex Among Apes" (1982) some parallel to humans and human societies became more and more popular. The term "Alpha" attained a kind of cult status when being used about humans, especially men: Everybody from ordinary, but more or less brutal social climbers to all men out to gain power wanted to be called "Alpha men", and those who didn't behave like driven by a wish for power were seen as "Beta men". The purpose of a man wanting to become an "Alpha" would be that he might have more chances of getting sex, but still, it's no guarantee that that would happen. One thing is sure, men took to the idea of "Alpha" and "Beta", not only in animal societies, but also in those of humans.

However, humans are more closely related to the Bonobo, than e.g. the Chimpanzee which should make us proud as they seem smarter and more social. For instance, they know to read the facial expression and behavior of humans. They, who don't live in Patriarchies, but in Matriarchies, have been found capable of altruism, compassion, kindness, patience, and sensitivity. As to "the leader of the pack" it most commonly is a couple of old matriarchs which one might call Alpha females, but it's a more or less meaningless term in this context. Actually, it is not useful to describe what's going on in a human society with terms like "Alpha" and "Beta", but some men, like e.g. Andrew Tate, clings to it as an important part of their identity. I fail to see anything "Alpha" in a man who, like Andrew Tate, resorts to sex trafficking and various sexual crimes to "prove" his masculinity. Chinless and probably lacking other male characteristics, he doesn't strike one as Alpha in any way.

Self-identified "Alpha males" like for instance Andrew Tate get very vulnerable when criticized for not being or looking what they themselves proclaim they are. Criticism is seen as an attack on their very personality, even though it's a construct like e.g. in Mussolini who strutted around, pretending to be some kind of Superman which he clearly wasn't.
https://www.calm.com/blog/alpha-male
https://greatergood.berkeley.edu/article/item/the_myth_of_the_alpha_male
https://www.discovermagazine.com/planet-earth/the-science-of-alpha-males-in-animal-species
Wikipedia