Perhaps less theory than fact.  Which, as you point out, doesn't necessarily reflect the talent of those who are conferred the honor, but perhaps the opportunities available to them.  The arts are often funded by charitable foundations, philanthropists, grant organizations.  In fact, Hemon's last novel has a character trying to get money from a private foundation to pay for his trip to Europe.  Anyway, often these people and organizations have agenda to promote this or that ideal, advance the success of this or that group.  I suppose having a tragic story helps in the acquisition of funds.  And I suppose some individuals feel helpless in the face of tragedy and want to make a difference in some small way.  I suppose some just want to make a solid karmic investment.  

And actually experiencing trauma like war or ethnic persecution etc. often drives people to write, create, to work through it, to "tell their story."  I guess it is possible for people with normal, privileged, safe, mundane lives to have something interesting to say.  But it's so much more exciting to read about people who have faces these character building obstacles and either overcome them or become martyrs.  [Kidding on the square.]  Also, the things that happen to Joe Blow down the street have happened to an individual.  Why should we care what he dreams about?  We all have dreams.  But if your people have been subjected to genocide, systematic racism, etc., your story balloons in significance because you are (we believe and no one corrects us) not just writing about your personal experience, but that experience of a whole "People."  Also, because of our collective guilt, we're also probably less inclined to be critical of such authors.  Like, we've done enough damage and should just keep our mouths shut now.  So no one tells Gary Shteyngart he's really not that great.  

All this said, Hemon really is that great.  Even if some people probably only read him or praise him or give him money because they're trying to deal with their own issues.  Ironically?, I'm fairly confident Hemon belongs to the "white, mostly middle class, slightly angsty and concerned audience which reads what's usually called 'literature'."

BTW, is Bosnian an "ethnic group?"  

Frankly, now that I think about it, I'm not even sure what an "ethnic group" is...

"Pretending that you already know the answer when you don't is not actually very helpful." ~Migeru.