I think a big part of understanding the answer to that question is understanding the concept of tribalism and how essential it is to the nature of Trumpism.
Tribalism is the basis of all the most primitive forms of collectivism such as racism and sexism (though it is broader and more fundamental than any of its specific forms). On the most basic level, it involves elevating allegiance to the group with which one identifies above all else.
Politically, we see this in the various Trumpian stances that attempt to single out and marginalize various groups who aren't on the 'approved' list: deporting illegal immigrants, objectifying women, banning Muslims from entering the country and infringing upon the rights of those who are already here, etc.
But there's a cognitive element to tribalism too: it consists of substituting group allegiance for one's actual thought and judgement.
Trump's supporters view themselves primarily as members of some group of which Trump himself is the standard bearer. How exactly that group is defined differs from supporter to supporter. It might be something like 'people who have gotten a raw deal at the hands of the establishment' or 'real Americans.' But however you define the group, its existence provides a handy cognitive shortcut: on any given issue or topic, you and the other Trumpies are right, and everyone else is wrong.
This substitution of group allegiance for rational, objective, principled thought explains a wide range of Trump supporter behavior -- including behavior that seems weirdly contradictory or hypocritical, for example
- Thinking that 'locker room talk' that objectifies women and even bragging about one's ability to sexually assault women with impunity is fine, yet having a problem if someone talked that way about your wife or daughter;
- Having a major problem with the serial infidelities of the spouse of your political opponent (and her alleged enabling thereof) while simultaneously supporting a candidate who is an open, unapologetic, serial philanderer;
- Being indifferent to Donald Trump's many documented lies and frauds while detesting Hillary Clinton for being 'deceitful';
- Embracing any conspiracy theory that tends to support your group's official line without any regard for standards of proof or evidence while simultaneously demanding evidence from your opponents ('show us your birth certificate!') that you are, in fact, determined to dismiss or ignore ('it's fake!');
- Expressing dismay at President Obama for overstepping his authority and dangerously increasing executive power while simultaneously supporting a man with obvious authoritarian views and tendencies who openly admires actual dictators;
- Heaping scorn upon Republicans who, whether for principled or pragmatic reasons, rescind their support for Trump while simultaneously giving Trump himself a free pass on the actions that caused them to regard continued support as untenable;
- Claiming to be a champion of American values while simultaneously advocating measures that would undermine them.
In all these cases, the sin isn't the actual thing. The actual thing is fine as long as a member of your tribe does it. The sin is not being a member of the tribe. The thing isn't right or wrong. Nothing is actually right or wrong. "Right" and "wrong" are useful rhetorical labels to apply to people and things to show your tribal allegiance.
The tribal mentality also explains the common (maybe the only) retort of Trump supporters when you point out their candidate's faults: the attempt at moral equivalence. 'So what if Donald used nasty language? Hillary tried to intimidate the women her husband had affairs with."
Do you see what's going on here? Its more than just childish tit-for-tat and playing fast and loose with the facts.
As long as we can pair off one of Trump's alleged failings with one of Hillary's, then they are equivalently bad. And if we can frame them as equivalently bad, then there's no objective basis for picking one over the other. No need to worry about pesky facts or arguments or the (sometimes legitimately tricky task) of wading through it all. We can now take the cognitive shortcut and treat it like a matter of personal preference, which is to say tribal loyalty. It's like rooting for the Yankees over the Red Sox.
It's why Trump supporters (even the tacit ones) don't seem to understand that people could have serious, profound concerns about a Trump presidency that, in their view, disqualify him from office. The thought of someone being disqualified on principle literally doesn't compute for them. They would actually have to believe there are such things as principles we could use to identify disqualifying behavior first. They would have to believe there are standards by which we could judge whether some particular behavior was disqualifying. They would have to believe in the value of evidence that would prove (or disprove) the existence of the disqualifying behavior.
But there are no principles. There are no standards. There is no value to evidence. There is only the tribe.