I'm going to just weigh in with my usual dark cynicism relative to your admirable buoyant and cheerful outlook that there are other factors in work than the authentic reactions of a spectrum of common people. Of course that is going on, and US democracy is not yet a complete and utter sham, but the layer of professional and highly situated cultural manipulators is a pretty old, established thing--Mark Hanna's approach to the 1896 election is already a case in point, then Woodrow Wilson hired professional ad men into the administration to manage wartime national narrative, and we just sink deeper and deeper.
Reagan's national image was very much a product of such manipulations--though as an artistic personality as you put it, I believe managing his own image was something he had a high degree of responsibility for. It was his forte. Now combining that with his tendency to say things that exhibited some combination of awesome stupidity, stunning levels or ignorance or sociopathic cruelty might seem paradoxical, but there is clearly something in the psyche of Americans, if not everyone in the world, that resonates with a smug bully on a roll, as long as you can identify with him and believe yourself to be one of the winners stomping a boot on the face of the losers, forever. It is the basis of what passes for right wing humor. I've argued before that the agency of common people is limited and constrained--this does not mean absent at all, but it takes both effort and risk for people who are not in the privileged inner circles of wealth and their hand-picked sycophants to act against the interests of the establishment. They can be mean and vengeful and quite over the top ruthless too--not typically judiciously so, unless the circumstances require it, but rather Custer-level massacre type mentalities. "Put them all to the sword for God shall know his own." It all is integrated into the Jacksonian mentality, whereby Americans who believe themselves in the wide but sharply bounded inner circle of "people like us who belong" believe themselves to be kindly and fair, if kind of crude and rough, among our own but that suspicious, ruthless vigilance is required against outsiders, and often "outsiders" are people who have been living among the circle of True Americans for centuries. People like us rejoice in the defeat and debacle of people like them, and a certain frontier toughness is assumed to be necessary. "We do not negotiate with terrorists" comes out of this mentality.
Given this streak of mass mind exists in the USA, professional manipulators know how to play it. Without both elements something like the Reagan Administration would have been unthinkable.
But with it, there is a dialectic going on between the manipulators and the manipulated. You might argue that it is patronizing to describe them like that, but I will mitigate by claiming the latter are playing a responsive part. They want their theatre and a successful manipulator knows how to deliver the kind of drama they want. If on the whole a certain political team is delivering the red meat of Jacksonian theatre, the circuses part, they will forgive high prices for bread and also the occasional misstep or false note. Think of a TV show you like that has had a couple real howlers of bad episodes; what you want (well, what I would want, generally) is for those to be forgotten, or set aside as special turkeys everyone makes fun of in good fun, and for the show to continue on the basis of what they did right, with those mistakes surgically excised from the overall image. This is the nature of the willing suspension of disbelief political dramatists such as Nixon to some great extent, Reagan almost entirely, and GW Bush and Donald Trump rely on. Political opposition that focuses on substance generally miss the point. Mind, as a person who isn't very good at lying and at this kind of political theatre I am talking about, I would hope there is an alternative path, a theatre of sincerity and openness and inclusion and sober working with real facts, that opposition can develop, but they err badly if they think it is just sufficient for the truth to be exposed and for a sane and sober majority to immediately take their authority as the People in hand and straighten out the Keystone Kops/Marx Brothers shenanigans running the show. It is not because people have the life experience of learning that truth and fairness are often light years away from how things work, and that it is dangerous to step out of line, and in that context want to be assured they are among the good guys. The followers of Right Wing political theatre believe that in the essence of the matter, their leaders are straight shooters. It may be that every word from their mouths is a lie and the reality they claim to believe in warped beyond recognition, but the important thing is that they flatter the masses into thinking they are all on the same side, and it will be the winning side because of their awesome goodness, and that their enemies are despicable scum who deserve a Death Wish like vigilante spree inflicted on them.
In this context nearly any crazy, stupid, heartless thing Reagan said or did would come across to his base the marks of a righteous man they are proud to stand with, just as Trump's admirers appear to see some kind hero where the rest of us...well never mind.
The homework of inverting the image of the Hearst family from grieving and terrified parents just like they would be to gibbering fools and wimps would be left to the audience largely, with just a few cues.
Another thing I often remark on in some puzzlement is how many of your PODs in these political WI TLs are actually exactly the thing that really happened, and the divergence lies in expecting people to react differently than they did. I think that layers of professional manipulation have to be considered, and the absence of countervailing cultural forces similarly organized (which the Right alleges actually does exist, and indeed that they are David to the Left's Goliath) is not an accident but the outcome of a carefully maintained cultural hegemony. To organize a counterattack an organization is needed, and the only candidates that historically emerged for that role, such as the Communist Party, were hamhanded and tin eared at this game, and easily discredited. (I contend that Marx and some of his followers were crackerjack economists and social analysts, but rotten at the game of pragmatic politics, and the tradition continues to this day. Of course today few read Marx as the powerfully insightful analyst of capitalist civilization that he was, and content themselves with simplistic formulas that despite their clumsiness are anyway no farther from truth than mainstream economics or social analysis tends to be).
The absence of the shrewd democratic populist, who can see both need and means of rallying the common people against the millions of Lilliputian threads that bind them to helplessness, might be due to some deep underlying nature of things and then I guess we are doomed to be playthings of this relentless riptide of privileged cynicism giving the mob the circus of inclusion and righteousness they crave. Anyway, the absence of a credible cultural center for speaking out the truth of circumstances is key to all of your questions of "why did it happen as OTL instead of this straightforward alternative I am talking about?" Note that there were always people saying the things you'd think would prevail, and you generally produce them as clear evidence you aren't just making stuff up. The question remains, why do they not engage the gears and shift the dialog over?
I'm telling you why. Cultural hegemony, that's why.