This is one show I never understood, the premise is so incredibly flawed and lends itself to only cast the most shallow gold-digging females and jerk men who don't mind going through a dozen girls hearts to pick one. And from what I can tell none of the couples on this show (not counting its sister show The Bachelorette) have actually gone through with it!
So he dumped her for the other girl, supposedly the reveal of this on the show was not a surprise, just filmed like it was. Big deal. They'll never last.