Why does Nick return to the Midwest in chapter 9?

At the end of The Great Gatsby (Fitzgerald), Nick is completely disheartened by his experiences in New York.  He says that after Gatsby dies, "the East was haunted for me..."(185). He believes that he is best-suited to the mid-west.  He muses over the happy times he has there, the family, the traditions, houses that remain in one family for generations, the stability, and even the bracing air of the long winters.  He says that Gatsby, Jordan, Daisy, and Tom, too, were ill-suited for life in the east, possessing "some deficiency in common which made us subtly unadaptable to Eastern life" (184). They were all unfit for the frenzies of the New York Jazz age, the frenetic pace, the lack of loyalties, the disregard for tradition, the anonymity. 

It is important, I think, to be aware that F. Scott Fitzgerald was born in St. Paul, Minnesota.  He lived in many places throughout his life, New York, Delaware, California, and France, to name a just a few.  But reading The Great Gatsby, one cannot help but think that Nick Carraway is expressing Fitzgerald's longing for the mid-west he himself had begun in, a mid-west that remained just a dream, since he died in Hollywood, California, writing screenplays.  Fitzgerald is kind of literary equivalent to Hoagy Carmichael, whose songs have the same plaintive longing for the same part of America.  There is good reason to call the mid-west the heartland of the country.