I've been thinking about it hard what do people find charismatic, attractive in Trump and Trumpism and I think I found an answer. I am certainly not the first—nor the last—to try at it, but here it is.
It is two fold—or three depending on how you count—, first his views on culture and such resonate with most even just slightly. His general ideas, that the system is rigged, that the American dream is getting further and further away, that crime—hear poverty here— is rampant, etc. The core of his ideas is simply engulfed in a thick layer of racism, xenophobia, ableism, homophobia, classism, etc. This makes it so that even if the primary message doesn't stick, the deeper one does. Slight tangent, but I do not think that he is aware of this, neither do I think he would accept such a framing.
Secondly, his unapologetic transgression of norms and rules. Or rather not directly this, but instead how he "keeps getting away with it". How one by one the institutions of society folds under him. This is the final blow that opens the door wide open to fascism in people's head. The door first weakened by his talks about resonating cultural grievance coupled with this. And the more insidious part, and actually why fascism spreads like a disease—from host to host, from person to person, transforming one by one people into rhinoceros—is that it is a self reinforcing loop. As institutions folds more institutions fold, because the people within them see that "he keeps getting away with it", working backwards to explain why it's happening—rather then going the straightforward way of "the people at the top of those institutions were weak minded"—they see those institutions folding as proof of the leader power, strength, mandate or even divine aura. Trump assassination attempt worked in the same way for many, a proof that he has some kind of aura or mandate of Heaven as they thought to themselves "he can't keep getting away with this", similarly with the dismantling of the US rule of law and constitution.
It is in that sense very reminiscent of those people who say of something outrageously dangerous and for which people are working to get it ban: "well if it was really that dangerous it wouldn't be legal in the first place (or it wouldn't have been created)", forgetting that regulation is reactive, not proactive. In a similar way, the liberal media apparatus became reactive instead of proactive, seeking news after they were uncovered rather than do the work to get them uncovered. And it is partly how he got here, the fourth pillar of liberalism folded without a squeak as they couldn't bring themselves to be proactive and attack first when their enemy was weak.
Fascism is on the rise, it works like a disease or dominoes toppling. Once the spread as started it is hard to stop, but not impossible—then we can search for a cure. And actually, stopping the spread is already dealing with half of the problem as fascism is a self reinforcing loop, once the loop is broken any small crack will make it crumble.
Addendum
Some other thoughts and framing I want to add
The same thing as higher, but written in a more familiar way with some additional thoughts
Fascism appeal and particularly its leader charisma is not charisma, but two things.
Saying so much stuff that statistically everyone can hear what they want or something that appeal to them. Either be it the solutions to the problems he points or simply the problem themselves.
And second a self reinforcing loop through which actor folding encourage others to fold because most people don't have strong political beliefs and so seeing their circles or society caving makes them doubt themselves and instead of being like 'others are wrong' they start to think that maybe indeed the leader is powerful, strong, he has good ideas, etc. Using the fact that people cave in as proof of the goodness of his ideas, but doing so encourages others around them to fold too.
And most importantly, it is to be confident. Even if confidently wrong.
It's why fascist leader are seemingly such fools. So stupid and that their appeal is almost impossible to grasp for someone with strong political beliefs that are contrary to fascism ideals. It's that it requires someone to be so megalomaniac about themselves, so stupidly confident that people start to doubt themselves. Some fool do so early thinking confidence = rightness while others need for their defences to be weakened by society caving in.
But the important thing is that it isn't manufacture confidence. The leader is not trying to fool people, he is the first fool to have fallen for his lies, for himself. There's no grand scheme to manipulate the masses and such, rather simply megalomania making it so that slowly by luck they create appeal. It isn't some carefully constructed persona, it is them.
That's something that annoys me with many analysis. The idea that there is an intent to manipulate in the way fascism does. But rather it is a mix of luck, megalomania and stupid overconfidence and luck is probably the most important one. Because starting the movement of fascism is hard, you need to have the right connections, the ability to have your ideas publicized, the financial mean to do that full time when your project is at its infancy.
Megalomania and overconfidence on the other hand are rather easy to find. And the ability to speak well or coherently is not required (I would say even a push back). How many people thought they had invented perpetual machine or whatever else that is so glaringly wrong?
People would like fascism to be hard, to require some villain with a clear intent to fool the masses, some form of genius who understand what he's doing. But it is actually the opposite. Someone doing everything by luck and guidance of his megalomania thinking it is his skill, when it is his lack of skills that makes him appealing. Otherwise he wouldn't be saying everything and nothing, he wouldn't believe in his own lies, he wouldn't be the person he is. It is just hard for people and society to accept that they got played by a fool, and not any fools, but the fool of fools, the one so confident in himself that he think he can never be wrong.