I like to believe that he launched his campaign for this purpose while expecting it to ultimately go nowhere, but it didn't work out like that. I don't think Trump ever expected to win the nomination and I am still not convinced he truly wants to do the job. He probably wants the position/title but none of the responsibilities.
I agree with this, especially the last sentence. His ego would love to have the title of President of the United States, but his temperament and other personal issues will have a hard time dealing with the actual reality of the job.
Plus, living in the WH would be a great step down from the lavishness he lives in now. That's gotta suck.