People trust leaders they vote for, according to studies discussed in "You really can fool some of the people, all of the time" (The Economist). "Because Mr Trump has abandoned so many traditional Republican policies, such as support for free trade and suspicion of Russia, the researchers concluded that it is personal: those who still call themselves Republicans support Mr Trump because of who he is, not what he stands for. And if personal loyalty trumps ideology, then voters may back a politician even if he does not tell the truth."
In addition, people aren't very good at spotting lies. Even people who should be, like cops, aren't. That's probably because we're born to assume that others are telling the truth. Why? Since most people tell the truth most of the time, it's more efficient to assume so. That is, if we had to check everything anyone says, we couldn't carry on the most basic conversations. And because we are hard-wired to assume that what we hear is true, we are therefore, says Tim Levine, author of Duped, "hard-wired to be duped."
And there you have it, the reason so many people stick with pResident tRump. "He's my guy & that's all I need to know." They're not lying!