I think a lot of it also has to do with "game theory." Game theory mathematics works in certain simplified games where your optimal strategy is to assume your opponent is rational. If the other party isn't rational, your optimal strategy works even better than if the other party is rational.
A lot of advisors and theoreticians etc are schooled in game theory and use it in places it shouldn't be used.
Problem is with complex real-world games, your strategy differs significantly if the other party is irrational.
FOX REPEATED JUST NOW: FIRED BY IRAN REVOLUTIONARIES
False, false, completely false. Strategies that work against a rational opponent may fail against an irrational opponent and vice versa. Consider a game with the following payoff matrix:
Player A | Cooperate | Defect | |
Player B | Cooperate | 500,500 | -10,-10 |
Defect | -10, -10 | -100, -100 |
This (extremely simple) game has a dominant strategy at (cooperate, cooperate). A rational player will always choose to cooperate; defection never gains him anything. Even if the other player chooses to defect, cooperation is the better move. But if the other player is irrational and chooses to defect, the rational player does worse than he would have done had his opponent also been rational.