This about crappy GM's plain and simple. I mean lets look at the multiple time all stars that have switched conferences in the last 5ish years.
Carmelo - Denver to NY
Love - Minnesota to Cle
Amare - Phoenix to NY
Gasol - LA to Chi
Howard - Orlando to LA
Rondo - Boston to Dallas (though Rondo is far from an all star level player at this point)
That is pretty much it. I mean I guess a guy like Garnett technically counts but he was so far away from all star play there is no point in mentioning him. Then you have guys like Al Jefferson going from the West to the East as well.
The reality is the Western teams have all pretty much just drafted better. Davis, Durant, Westbrook, Kobe, Duncan, Leonard, Aldridge, Lillard, Curry, etc.