I don't think it was meant to go on as long as this but i think they kept it going because Frankie was in danger and it's easier to manipulate situations with the BOB still in place.
I was also amazed that they let Frankie and Christine leave the house to go to a football game!!!! Wouldn't be surprised if that was so Frankie could have a meet-up with his people.
So yeah, the BOB has been awful for the Season but i think putting in a houseguest like Frankie who potentially has a load of his sister's fans that will get behind him so even if he does get evicted they'll probably decide who gets to go back in via a public vote.
Also for him, when he realized how much he was in trouble in there, to be allowed to suddenly come up with the lie that he's playing for charity to build schools for poor African kids in an attempt to emotionally blackmail the other houseguests into not evicting him is absolute bullsh*t!!!
Terrible season that's only getting worse!!!