Why Have a King and not A President?
Simple. Because they wanted to prop up a ruler over the land and a democracy would keep Sauron as it's clear he had more support.
I can't believe how a movie like this isn't regularly called out for the propaganda it is.
Clearly a leftist flick. A diverse ensemble of characters invades Sauron's land, slaughter his people, and notice how 'the trees' react to Sauron's technical achievements and attack his fort. Clear pro-earth propaganda!
I am the prophet of the IMDb Mod Gods. They act when I call.