My guess is that the Nets are looking at him as a sixth man/spot starter and the Kings were looking at him as a situational 4th big. That and I'm guessing Bargnani actually likes living in NYC and playing in Brooklyn he can keep his existing place.
Either way I'm fine with Bargnani not being on this team. Vlade's been putting together a very tough minded and passionate team and while Bargnani would bring a needed element as a shooting big, I'd just as soon get a lunchpail type to be our veteran PF.