Because they cannot fathom a person not caring what other people think of him, as long as he achieves a goal that is so much larger than self. They cannot understand anyone putting themselves in harm's way for the greater good.
I remember Krauthammer from the days I was still watching FOX. He was talking about being at a dinner at the WH with Reagan, and he asked a very pointed question about something serious, I can't remember what. Reagan started to act a little flakey and talk about the crown moulding or something. Krauthammer either mentioned or I was thinking, "he'd rather look like a doddering old man to a nationally syndicated reporter and deflect, as long as he gets what he wants." Which in that case was to successfully avoid answering the question. Given that I trusted Reagan I assumed it was information he didn't think Krauthammer could be trusted with (who knows anymore). I was thinking at the time that only a man who believes in and loves God and can withstand that short term humiliation and forego reward, even if it has to come in heaven.
I have long believed that Trump's carnival barker act honed during the "Your Fired!" years is part of an act and part of the plan. He was always blunt for sure. But not always as exaggerated or cartoonish. He has turned politics into a verbal WWE match at least for the short run. I think this persona was needed as the first jolt to awaken the masses. We needed to be shocked out of our collective stupor. Obviously, it didn't work on everyone LOL. But seriously, look at all he has accomplished. He has decimated fake news. Absolutely demolished in less than a decade. Newt Gingrich was trying to humiliate, but his comments although direct, didn't garner the same attention. I recall years ago hearing that an advertising jingle can be annoying and very effective, as long as it is memorable. Even people who thought it was outrageous and obnoxious for Trump to point to CNN or individual reporters and call them "Fake News!" couldn't help but remember that he said it. Mission accomplished. A huge swath of them not only believe it now, they KNOW it to be true. Same with "Crooked Hillary" and "Low Energy" Jeb, et. al.
The once revered FBI is in shambles. Because RUSSIA RUSSIA RUSSIA! and "Witch Hunt!" That one took awhile. Politicians were never revered, but both sides of the aisle pretty much accept that they are all crooks.
Trump is one of the most interesting public figures of all time to me. I don't think anyone but the people closest to him really know him.
Side note, I have wondered if Charles Krauthammer would have changed from a never Trumper if he had lived to see all this.