Why do Trump supporters (estimated at 33% of the electorate, on the high end) so sure he is right and speaks the truth?
The falsehoods and lies are real, checked not just by factcheck services that have come into existence since most media cut its one fact checkers for the payroll, but by historians, member of the supreme court, fellow Republicans, most all university researchers, and most reporters doing any digging at all. Trump lies. It's that simple.
There is no past president in trackable US History who has lied or spoke falsehoods more time than President Trump. He has 25 times as many falsehoods as any previous president (Nixon held the Record up until Trump).
Unlike previous presidents, who passed on falsehoods in the name of National Security and later provided the facts supporting why they did, Trump speaks out on things that have no reason for release and still looks back and reuses the statements from his campaign that no longer have any effect on governing.
During the campaign Trump was caught in lies and major distortions ten times at Politifact's Pants on Fire extreme level.
Does the "media" tell the truth.
First of all media is the way you receive the information, not a single journalist or source publication or broadcast.
Second, much of the "media" are talking head "experts" paid to say things that get response from an audience that sells papers, keeps people watching on the Internet, or keeps them in six minute increments on television and radio. Others are commentators, whose job it is to have an opinion, one that will elicit response (not main stream there). That is not journalism, although journalistic content may be presented.
Journalism and reporters are trained to get both sides of the story, to ask solid questions, and put information together in a way that reports on what is happening. They are also the Fourth Estate, meaning they have a constitutional duty to keep watch on and report on the actions of all three branches of our government and its members / players.
Not all information has the same value. Not all is accurate to the same degree. Not all information is fact.
Russia did fund and even produce Internet and video video products without revealing they were behind the deliberate falsehoods, repeated as fact on the Internet, by believers who want to believe the information and Trump himself. The Clintons ordering people killed, Hillarys various illnesses, an inflated presentation of both North Korea and Iran's current nuclear potential have all been traced to Russian operatives with no facts uncovered.
Journalist need to do their job.
Call a lie a lie, a mistake a mistake, a falsehood a falsehood, fabricated news "fake".
It is their job.
And find the truth behind why actions are taken and when, what happened, who reported it, their credentials or position in the story and on the relation of that information to larger issues and stories.
That does not mean revealing the names of all your sources. But that is a different commentary...