President Trump is a brazen and shameless liar. His healthcare statements while running for president were totally incoherent and he casually made up facts. He made promises everybody knew were unattainable, such as Mexico paying for his border wall and boasting that he would pay off the federal debt within eight years while dramatically cutting taxes, boosting military spending, and not touching entitlements. Yet he won.
A reason for that could be that Clinton and Romney were in many ways standard lying politicians who took positions based on what would be most politically beneficial at a given time and came off as inauthentic (though Clinton was more corrupt).
In contrast, Trump’s often long and meandering campaign speeches actually came off as unrehearsed and natural. He was willing to dig in on controversial positions unapologetically. He challenged the orthodoxy of the Republican Party on trade, immigration, and foreign policy so he didn’t come off as pandering, even though he reversed his old liberal positions on abortion, guns, taxes, and healthcare. His base supporters thought he “told it like it is” and were distrustful of the media and thus any fact checks. And actual media errors just provided Trump with more justification.