As much as people have turned against him and the boos and get John out chants , he is a major talking point and people do have an opinion on him. Seeing as it's vote to save you will have to vote for the other 3 to get him out which is not going to happen. He has a role : the villain. Which will polarise voters in those who love him and those who hate. Those who hate cannot get him out as its not a head to head.
Whereas who really is going to vote for Kristina? She's done very little apart from pregnancy announcement. She doesn't have a fan base, Strictly fans really hate her for her Siberian Siren husband stealing ways. Daniella is just there as well.
John and Tiff will top the votes I suspect.