So I have read the thread and here is what I think.

First there is no point in guessing why the mafia targeted Kuja. They did and that's it.

Second we should not speculate at all on our power roles. Mafia do have a roleblocker so if the doctor claims then the doctor is useless. Same with the cop, I think he or she should only claim if the investigation came up mafia or if we are heading for lynching a town.