I'm not surprised at this, given Kirk's long association with Mantello (I can't believe how long ago it was I saw Love Valour Compassion!) and his stage experience.
Logistically, of course, it would have been tricky to wait until after Risch settled into the role before deciding whether to stay with him or bring in someone new in January. This way Justin Kirk will have enough rehearsal time with the rest of the cast.
This kind of long-range planning also suggests that Other Desert Cities is settling in for a substantial run, probably in anticipation of Tony attention.
"Sweet summer evenings, hot wine and bread /
Sharing your supper, sharing your bed /
Simple joys have a simple voice:
It says why not go ahead?"