The uses that a regime is put to are one thing, The methods used to establish and maintain the regime are something else. Saddam was a hard core Stalinist in his methods of achieving power, not his uses of that power. And, no, all religions were not free to flourish. Shiaa pilgrimages like the current one were repressed, for example.
Why failed? In several places the spread of Communism was stopped by the US supported dictatorships. Would you have rather have Latin America to be ruled by Che Guevara?
Failed because Communism would have never been feasible at all with functional democracies in Latin America instead of the US supported Kleptocracies. Without a Batista, there would have been no support for Castro. Without the corruption of South American Generalissimos, Che would have been a mediocre country doctor.
The Iran fell to Islamists after dictator/shah was abandoned and Vietnam started to fall to Communists after Diem was killed with approval of Kennedy.
The key words here are "abandoned" and "killed". Poor policies that left a power vacuum. Democracies don't spring into vacuums; they have to be built and nurtured.
Human nature did not change. BTW, Democracies/republics existed before 1705 and EACH time if allowed to last long enough and prosper they evolved into monarchies/empires.
Most were not democracies or republics save in name. They were in fact oligarchies, where the power to vote was retained only by the elite (a mistake we almost made, but thankfully remedied).
This is not so black and white. In USA the universal became the norm only in XX century and it did not necessarily correspond with the strengthening of the republican system. And very few if any people in position of power in US are recruited from the lower class. I assume that most of leading positions are occupied by the rich.
BTW, in local government when the salaries are restricted to symbolic low level only rich can afford to be in the office.
Most were not democracies or republics save in name. They were in fact oligarchies, where the power to vote was retained only by the elite (a mistake we almost made, but thankfully remedied).
This is not so black and white. In USA the universal suffrage became the norm only in XX century and it did not necessarily correspond with the strengthening of the republican system. And very few if any people in position of power in US are recruited from the lower class. I assume that most of leading positions are occupied by the rich.
BTW, in local government when the salaries are restricted to symbolic low level only rich can afford to be in the office.