Trump is not brillant and lied about his grades and class standing

On a personal level, we know that Trump is desperately insecure about his intelligence. People who are actually smart don't go around telling you how smart they are, but Trump regularly feels it necessary to proclaim himself a genius; here's a representative stream-of-consciousness soliloquy from 2016, which actually began as a rumination on nuclear weapons:

Look, having nuclear — my uncle was a great professor and scientist and engineer, Dr. John Trump at MIT; good genes, very good genes, OK, very smart, the Wharton School of Finance, very good, very smart — you know, if you’re a conservative Republican, if I were a liberal, if, like, OK, if I ran as a liberal Democrat, they would say I’m one of the smartest people anywhere in the world.

The subtext of Trump’s repeated claims to genius and his criticisms of Obama was that electing him would replace the falsely intelligent and undeserving president (Obama) with an actually intelligent and deserving president (himself).

By 2016, that was a message the conservative base was eager to hear. They’d spent the previous eight years being told by media figures such as Rush Limbaugh, Bill O’Reilly and Glenn Beck that Obama’s entire presidency was oriented around showering benefits on lazy, undeserving black people while whites were marginalized and discriminated against. From hoaxes such as “Obamaphones” to the repeated claim that any policy initiative Obama pursued was “reparations” aimed at taking money from white people and giving it to black people, the voters who became Trump’s base knew this story well.