We can use EZNEC to simulate the radiation of a coax with a wire as
suggested in the help file "The radiation properties of a coaxial
feedline can be modeled by connecting a wire of the coax shield's
diameter to the point on the antenna where the shield connects."

We then see that the current has a maximum somewhere along that wire.

My question: Why do we have a maximum? Is is because some current is
also going up from the source outside the coax?, In that case, some
kind of constructive and destructive interference could happen on the
outside of the coax due to phases differences between the two
currents, creating maximum and also nodes.

Or is there another reason explaining that maximum?