It's almost the same question as asking how a rational (etc) person can believe in Christianity.

Actual Truth? It goes all the way to our biology and evolution. It has to do with how organisms identify as self and not-self. Not-self is recognized as 'other' which is either indifferent or a threat.

Humans are borderline colonial organisms and as such, willingly give hypnotic allegiance to a leader. This occurs to people who are indoctrinated to identify with a particular group. See how GOP disregard Putin's control if it means not giving in to Democrats. Trump wants to be the King Bee. The problem is, for those not hypnotized into his personality cult, his faults are many and varied. Those who gladly swear fealty turn a blind eye to all of it. Democrats have always been the target of their hatred; Communism was only an evil with which to tar those Democrats.

There is also some major psychopathic schizophrenia where loyalty erects a wall between ordinary practice of ethical behavior versus applying those values to the King-Bee (or Church leader). There is significant fear of rejection by ones cohort if even the slightest question is raised against republican (or Christian) dogma.

True Believers play the Liar's Club game: who can tell the biggest fib. It's the Emperor's New Clothes writ large, and we are all forced to watch Donald's junk bounce and sway. Even now we see on a daily basis GOP politicians spitting out the most idiotic excuses for Ukraine. The moderators can only stifle their cringe and change the subject.

Few people have the courage to question or object to the values held by their friends and family, even when those values are easily seen to be corrupt. Thus, to object to the leader means a rejection of ones own identity. The singular ant is on it own, and woe to it if it ever runs into its former fellow ants.

Humans pride themselves on having free will and consciousness, but that is sheer hubris. People readily abandon their lives to shallow programmed behaviors, and are far from having the horsepower to meaningfully contemplate themselves, others, or anything at all.

The real problem is the same one created by the election. We have a certifiable psychopath with his finger on the button.

Most intelligent and rational people don't support him

Here's another article, this one emphasizing cultural anxiety:

[theatlantic.com]

Trump has done a very good job using identity politics, appeals to his base specifically as white Americans. The details are a bit different than we often are told:

[theatlantic.com]

There were trump supporters, and are trump supporters.

The first ..at best, I’d describe as single issue voters, incapable of recognizing or understanding his potential damage to the spectrum of issues facing the world.. I hope he’s lost ‘those’ folks. And, those I know ..are unimpressive as people, misfits, angry, more looking to ‘bring down the system’ than improve it.

The second set, his current supporters - have zero redeeming values. They are the type of scum most civilized societies do not allow to congregate, let alone assume power.. The pawns of industry, they’ve become the overly-armed shock-troops or Brownshirts of the new extremist Republican Party. They are would-be Nazis (period)

So don’t feel bad about an inability to embrace either of this crowd. Be proud you’ve the inner morals and integrity to be repulsed by them.

in my experience when dealing with people who are otherwise seemingly intelligent and American I have found the Trump supporter to be a worshipper of money. it's really that simple and that ugly. much much worse than a religious zealot who denies a lack of evidence, the Trump supporter denies the mountains of evidence indicating how this man is trash and is doing his best to trash our nation. they trample on the sacrifices of those before us and call it patriotism. they are a twisted lot.

While I agree with little of their views, I like to confront myself with the opposition as a way to ensure my arguments (in the ameliorative sense) are not easily falsified. In doing so, I occasionally encounter some rationality.

It's becoming untenable watching the batshit bingo card fill up - and people still are defending the most bizarre of his actions - I'm pretty sure this happened during Nixon's impeachment too?
Even as a child I was aware of what was going on to some extent and there were those still saying he was a good man. So I think this has happened before - just not with so much film of the poor decisions made.
I'm pretty sure I'm past make bingo and into triple Yahtzee scoring though?

A blurb in your bio might help, but I would suggest putting it early in your bio, so it shows up in the popup mini-profile.