The hope was that three tribes would prevent another Pagong after the merge. This has been a problem in recent seasons because contestants after the merge have cheerfully let themselves get voted off without a fight, or in some cases with a hopeless last minute scramble. They don't try to make new alliances after the merge and cower at anyone who might have an idol. Another solution would be get smarter contestants but that's crazy talk.
Of course they didn't expect one team to suck this much. They probably thought Russ could easily carry the entire tribe on his back.
Russ reminds me of those super-ripped guys who sign up for marathons, then around mile five you see them doubled over on the side of the road throwing up on themselves.