re: Was it Smart and his staff or did the pieces fall into place?

Last season would not have been as successful without Chubb, Michel, Bellamy and Carter. All four of them staying for their senior season was huge, both in terms of production and in terms of leadership.

All four were Richt recruited players who played two years under Richt.

IMHO, if Richt was still HC at Georgia after an 8-5 2016, I don't believe that any of the four would have been at Georgia in 2017. So in that sense, some if not all of them were in fact Kirby players, who wouldn't have been on the roster if the predecessor was still there.