Why is John's confession so readily believed by Danforth

I assume you man at the end when he confesses that he has seen the Devil. Rev. Danforth wants a confession whether it is a lie or the truth. Danforth just wants proof from a member of the community like Proctor that the Devil was indeed in Salem. Proctor's confession would validate Danforth and his court. His confession would justify the hangings of all the people that Danforth had condemned.