It was something of a no-win situation for the producers so they went for the lesser of two evils. That is to say they intervened excessively to stop the 'baddies' picking off all but one of the 'goodies'.

Whilst a lot of people may not care (or even admit that's what happened), for me it was unsatisfactory although obviously I quite understood why they did it. It just reinforces the point that production decisions have a huge influence on the outcome (who-stays-they-decide-too) which completely undermines the contest aspect of the show.