One (admittedly) very small but yet classic example of how Trump is driven by his petty and vindictive emotions rather than by being well-informed is his threat to overturn the 2015 decision by Barack Obama to change the name of Mt. McKinley in Alaska to Denali. Curiously, Trump said this was an insult to the people of Ohio (President McKinley's home state)... even though Mt. McKinley is obviously in Alaska.
After taking office in January of 2017, he was determined to quickly follow through on this pledge and reverse the name of Denali back to Mt. McKinley. It was the two Republican Senators from Alaska, Dan Sullivan and Lisa Murkowski, who had to explain in a meeting with Trump that Denali was the name given to the mountain by the Athabascan people more than 10,000 years ago and plead with him not to change the name back. Trump was completely ignorant of the history of this great Alaskan mountain. He simply wanted to reverse an Obama decision, just because it was an Obama decision. He took no time to educate himself as to what was important to the people native to Alaska.
I know it's not a big deal but in a very small way, it is classic Trump. Ignorant, petty and vindictive.