(A) "Collusion" is not a crime. Even if there was "collusion," it was likely no big deal. Someone on the Trump campaign spoke with Assange, and concurred with the dates of their data dump. Collusion? Probably. Criminal conspiracy. NFW.
(B) The definition of "The Trump Campaign" can be very broad indeed. Formal, paid advisors, informal, unpaid advisors, advocates in the Media (e.g., Ann Coulter?). Trump himself may not even be aware of some of the people who might later be considered as part of his "campaign staff."
(C) No one could ever confidently say that no one connected with the Trump campaign ever "colluded" with anyone even remotely associated with the Russian government. The possibilities are simply too broad.
(D) Guiliani's recent statement simply covers that possibility.
No. Big. Deal.