Narcissists... No doubt Trump is one of them. One of the reasons got elected because america celebrates people who celebrate themselves.
I think narcissists are very frequently in positions of power because they know how to manipulate others and make themselves seem infallible....
it's an offence to even suggest they might be wrong, so people around them become yes-men just to avoid conflict, giving them reinforcement in their narcissistic beliefs.
Then one of them seizes power, it's Ok because it's their god-given right to rule over lesser humans. It's no surprise that they create a cult of personality around themselves.