One suggestion was that the court was the least busy federal court around (all the other federal courts were swamped with drug cases). So patent cases started appearing there. Once the judges in the area became so-called "experts" on it, more and more companies started to file their cases there.

NPR (well, technically This American Life) did a special on it a couple years ago[0]. It's fun to listen to. It may not tell the whole story, but it at least paints a decent picture.

[0] http://www.thisamericanlife.org/radio-archives/episode/441/w...