Let's say the roles were reversed though. Ali, Emma, Hanah and Marcello were put in The Vault. How would that have worked out?
My point being BB made the choices. Not the public nor the HM's. For all we know Marcello might have had less public support than Sarah at that point. So if he had entered The Vault he could have possibly gone. In my mind it was well thought out to get the best possible result in the producers eyes because only they know the public opinion and how they want to push that.
I don't like it when the choice is left to the powers that be.
What happened to democracy?!