Trump isn't studious, he isn't meticulous, he isn't detail or fact oriented. He sees what is fed to him and believes it. He hears that Chicago has a growing murder rate and thinks, this isn't what it was before so it must mean that it's the highest in history. He sees a story about voter fraud and thinks that there must be a reason why he lost the popular vote. He hears that crime is high and thinks that it wasn't that way when he grew up so assumes it is the highest it has been in the last 40-50 years
He sees a huge crowd at his inauguration and thinks that must be the biggest crowd I've ever seen and can't imagine a bigger one, so he tells everybody it is the biggest one he hears one story about Mexicans coming across the border with bad intentions and assumes they are all the same.
He's like the old timer at work who tells you that in his day they'd ship 1000 shipments per day even if the sales number back then don't confirm it, the father who said he walked in foot high snow to school every day. The story you tell your kids today about playing outside every night until dark which probably happened sometimes but you were home watching tv a whole lot, too.
It's not all bad intentions but it's what you see, what your own biases tell you and what you choose to believe. Not a bad way to live through life but a terrible way to set the nations agenda. See Trump lives in an anecdotal reality, he believes what he sees and reacts off of it.