> Everyone is always acting game-theoretically optimally.
This isn't true at all. The fact that the efficient market hypothesis doesn't seem to hold is already the proof of that, and the same reasoning applies to other social behaviors [4].
Furthermore, many, many, many, many studies in neuroeconomics and behavioral economics (and related fields) [1] have shed light on the bounded rationality of human actors in decision making. Game-theoretically optimal decisions is a specific, well-defined thing that's different from making decisions based on the affects and biases of the preconscious and unconscious. You can't just tautologically define "game-theoretically optimal" to be whatever decision someone ends up making.
What does this mean? The direct implication is that it's neither game-theoretically optimal nor inevitable for stateless humans to enter into a social contract that eventually cements itself into a state apparatus.
A top-down authoritarian doesn't get their powers from a deity, yes, but it wasn't quite explicit coordination either. To demonstrate using a brief example, one of the models of the evolutionary stages of the social contract [2][3] is that states were a natural conclusion of tribal societies, which were themselves a natural conclusion of lineal societies, i.e. families. Lineal societies most likely weren't formed through explicit consent, i.e. early stateless infants probably didn't explicitly decide to enter into a social contract. There's basically no particular a priori reason why families exist (for example, the Ik people in Uganda seem to have no or a very weak concept of using familial relations for survival, even to protect their young), and very likely that this evolution was just the model happened to win out due to random noise in history rather than actual optimality.
Again I would like to stress how much the current societal configuration is mostly just noise instead of signal.
[1] For an introduction, https://www.goodreads.com/book/show/11468377-thinking-fast-a...
[2] https://mitpress.mit.edu/books/nomadology
[3] https://www.goodreads.com/book/show/118317.Anti_Oedipus
[4] http://slatestarcodex.com/2017/11/30/book-review-inadequate-...