What is the real reason why Trump didn't attend Biden's inauguration?

He is a crybaby.................

Because it wasn't about him.  If it isn't about him, he isn't interested.  

Because he lost.  It was supposed to be HIS inauguration.

Because he has the mentality of a toddler and can't accept the loss.  He threw many tantrums to show he has no morals, ethics or even sense of decency as was witnessed by the whole world on Jan. 6th..  The world and history will not forget this treasonous and vindictive president.  Not to mention lying sack of shiat.

Because it would have been equivalent to admitting that he is a loser.

Trump considered Biden unworthy successor, till the very end he considered Biden weak.

He literally cannot stand it when someone besides himself is the center of attention.

He knew it would be a farce for him to do so... not to mention totally disruptive. 

Because he is a cry baby. 

Because he is a snowflake with a fragile ego which is unable to accept reality.  It is a mental health issue.