I'm pretty sure it's supposed to be a mockery of misogyny (or the more general toxic masculity). The Sigma male term was supposedly describing a social outcast who doesn't play the social game but still somehow wins the social game, and thus gets respect and women. Obviously the internet ran with it because it hits the sweetspot of stupidity where it becomes funny

Of course some people actually believe it and use it unironically, but it's mostly about mocking the supposed Greek lettered male classification. Then again memes change in time and maybe it is returning to its original toxic meaning.