It's very hard to feel sorry for those Republicans (and Right wing journalists) who are shocked at the continuing popularity of Trump, when they did nothing for years to tell their nutty base that they are nuts.
As David Corn says, it's not as if the evidence for the nuttiness has been hidden:
Republicans are pissed off. (In polls, they express far more dissatisfaction with the nation's present course than Democrats.) And they believe the nation has been hijacked by President Barack Obama, whose legitimacy most Rs still reject. A recent Bloomberg/Des Moines Register poll of likely Iowa caucus participants found that 35 percent of Republicans
believe Obama was not born in the United States. A quarter said they were not sure. (Nine out of ten Democrats said the president was born in the United States.) So nearly 60 percent of Rs believe there is cause to suspect Obama has hornswoggled the nation. Meanwhile, according to
another poll, 54 percent of Republican voters say Obama is a Muslim. A third were not
sure. Only 14 percent identified the president as a Christian.
These findings—which echo a long string of surveys conducted during the Obama years—would seem to indicate that at least half of the GOP is unhinged and living in its own fact-free and perhaps Fox-fed reality. To top it off, many Republican voters have expected the GOPers in control of Congress to kill Obamacare, shut down the government and slash the
budget, prevent Obama from issuing executive orders, and impeach the pretender who inhabits the White House. Oh, and there's this: Benghazi! So they are mighty ticked off and seriously disappointed. The Bloomberg/Des Moines Register poll found that half of GOP caucus-goers said they were unsatisfied with the US government and 38 percent were "mad as hell" at it. Slightly more than half were unsatisfied with Republicans in Congress; a fifth were mad as hell at them.