His Own Reality Bubble

The fact that when giving off the cuff/unprepared remarks Trump’s thoughts are jumbled and unfinished proves that he needs someone to write his speeches for him. 
The problem is that he tends to wander off the prepared statements back into his own ramblings. I don’t think he can help it. He could fully intend to follow the speech but decide to make his own comment about something in the speech and suddenly he is off to the races.
Either that or he refuses to use a prepared speech at all. His whole “I’m the smartest man in the room. I can handle talking about this better than anyone here.” is always his downfall…for anything. 
Of course he also lives in a bubble of people telling him that everything he does is fantastic and that he did a good job with this or that regardless of the reality.