Milius was famous for being a macho force in Hollywood. He wrote Dirty Harry, Apocalypse Now and consulted or worked on other films, adding a touch of machismo when needed. The man wrote Red Dawn, which is the most pioneer themed, libertarian movie of the last 30 years. Milius used Conan as a skeletal structure to act out the '80s fantasy of revenge on the forked tongue professors and cult leaders of the prior decade. Milius' view would be that a strong willed man of traditional, masculine powers could decapitate (literally) those Pied Pipers and end that sick force of liberalism. Spoiler: the movie ends with Conan doing exactly that, and the followers of Thulsa Doom just toss their candles into the water and melt away.
Think of the entire movie. Thulsa Doom's Set cults are spreading. Youngsters tricked into following them stab their parents. Thulsa Doom talks of destroying the old order and elders:
You, my children, are the water that will wash away all that has gone before. In your hand, you hold my light, the gleam in the eye of Set. This flame will burn away the darkness, burn you the way to paradise! ... Purging is at last at hand. Day of Doom is here. All that is evil, all their allies; your parents, your leaders, those who would call themselves your judges; those who have lied and corrupted the Earth, they shall all be cleansed
Holy shit, does that sound straight from the mouths of far leftist cults from the '60s and '70s? The old king sends Conan and his crew to bring his daughter back who turned away from him to follow Thulsa Doom. Thulsa's cult has tons of hedonistic acts going on, and Thulsa himself while portrayed by James Earl Jones has the odd eyes and hair that one might associate with Eastern Gurus. How many white kids seek enlightenment with gurus and communes pre-'82? Does the king's daughter, brainwashed by Thulsa, remind anyone else of Patty Hearst and the Symbionese Liberation Army with its cobra symbol? Good old Conan will set everything right with some ass kicking. Your hippies words will mean nothing compared to some fighting.
Milius was wrong. You cannot just decapitate the snake of '60s/'70s liberalism and set everything right. Thulsa's words found fertile soil. In a real world, killing him could not simply stop the idea or rectify the troubling environment that gave rise to him. Conan spoke to regular action audiences because it was the big guy destroying the weaselly, different guy and saving a princess for the existing order. In the climate of 1982, Conan was reaching a little deeper into those moviegoers minds and telling them, "We can just be rid of their visible leaders and all will be right again. Your children do not hate you if you just use enough force and have a superior champion on your side". Audiences watching it, especially proles not able to go to college in the '60s and '70s, might have given that revenge fantasy a thought but quickly tucked it away. Best not to think about what those cultists are doing now since you never eliminated their leaders.