The main reason is the Monroe Doctrine. The United States literally made it its business to terrorize any "communist" state, even if it's democratically elected. That breeds the conditions for paranoia, the desire for increased protection, etc.
But, in the context of endgame scenarios against dictators, the main factor usually is how the military responds, especially when asked to brutalize the population. If the military parts ways, they may start a coup of their own or they may (rarely) defer to the population.
So, by extrapolation, I imagine it's also true here: other powerful factions allow it because it opens opportunities for them to garner more power too. Business execs, politicians, and military officials alike are duking it out for influence amongst themselves as well.