It is a human characteristic to be in denial over a shocking event. Some people have to go through a period of denial when their partner suddenly dies, or they have been diagnosed with a deadly disease. But denial is usually limited to a certain time period, until the unavoidable reality sinks in.
But narcissists can be different. They have problems being confronted with reality and will stay in denial for good.
Trump is such a person. Trump cannot lose. Trump is a narcissist. If he loses he's gonna "die". At least that is how he feels, and that is the reason why he won't accept his election loss. For his part, I am not surprised.
What is more astonishing is that the GOP still hasn't realized that they are passengers on a sinking ship. Trump is gonna be entirely useless for them and if they wouldn't have nominated this moron, they could have won the election fair and square. Well, denial can be a bad thing, as it leads to disastrous decisions. The future will show them where they went wrong.