It was the first presidential instance of what the campaign regulars had learned over many months: on the most basic level, Trump just did not, as Spicer later put it, give a fuck. You could tell him whatever you wanted, but he knew what he knew, and if what you said contradicted what he knew, he simply didn't believe you.
The book "Fire and Fury: Inside the Trump White House" by Michael Wolff reveals a significant aspect of Donald Trump's approach to the presidency. It discusses how, over the course of his campaign, it became clear that Trump was largely indifferent to the traditional advice or insights from political experts and campaign professionals. His attitude was characterized by a strong sense of self-belief that overshadowed any external input.
According to former press secretary Sean Spicer, Trump's disregard for opposing viewpoints was foundational to his decision-making process. Trump’s confidence in his own understanding led him to dismiss information that contradicted his beliefs, suggesting a disconnect between him and more conventional political strategies. This fundamental aspect of his personality shaped his presidency in unique ways, emphasizing an unfiltered, self-reliant approach to governance.